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The Formation and Evolution of M33 as Revealed by its Star Clusters

Permanent Link: http://ufdc.ufl.edu/UFE0043990/00001

Material Information

Title: The Formation and Evolution of M33 as Revealed by its Star Clusters
Physical Description: 1 online resource (323 p.)
Language: english
Creator: San Roman Aberasturi, Izaskun
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: clusters -- content -- galaxies -- m33 -- stellar
Astronomy -- Dissertations, Academic -- UF
Genre: Astronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Numerical simulations based on the Lambda-Cold Dark Matter (Lambda-CDM) model predict a scenario consistent with observational evidence in terms of the build-up of Milky Way-like halos. Under this scenario, large disk galaxies derive from the merger and accretion of many smaller subsystems. However, it is less clear how low-mass spiral galaxies fit into this picture. The best way to answer this question is to study the nearest example of a dwarf spiral galaxy, M33. We will use star clusters to understand the structure, kinematics and stellar populations of this galaxy. Star clusters provide a unique and powerful tool for studying the star formation histories of galaxies. In particular, the ages and metallicities of star clusters bear the imprint of the galaxy formation process. We have made use of the star clusters to uncover the formation and evolution of M33. In this dissertation, we have carried out a comprehensive study of the M33 star cluster system, including deep photometry as well as high signal-to-noise spectroscopy. In order to mitigate the significant incompleteness presents in previous catalogs, we have conducted ground-based and space-based photometric surveys of M33 star clusters. Using archival images, we have analyzed 12 fields using the Advanced Camera for Surveys Wide Field Channel onboard the Hubble Space Telescope (ACS/HST) along the major axis of the galaxy. We present integrated photometry and color-magnitude diagrams for 161 star clusters in M33, of which 115 were previously uncataloged. This survey extends the depth of the existing M33 cluster catalogs by ~1 mag. We have expanded our search through a photometric survey in a 1deg x 1deg area centered on M33 using the MegaCam camera on the 3.6m Canada-France-Hawaii Telescope (CFHT). In this work we discuss the photometric properties of the sample, including color-color diagrams of 599 new candidate stellar clusters, and 204 confirmed clusters. Comparisons with models of simple stellar populations suggest a large range of ages some as old as ~10 Gyr. In addition, we find in the color-color diagrams a significant population of very young clusters (< 10 Myr) possessing nebular emission. Analysis of the radial density distribution suggests that the cluster system of M33 has suffered from significant depletion, possibly due to interactions with M31. To further understand the properties of M33 star clusters, we have carried out a morphological study 161 star clusters in M33 using ACS/HST images. We have obtained, for the first time, ellipticities, position angles, and surface brightness profiles of a statistically significant number of clusters. Ellipticities show that, on average, M33 clusters are more flattened than those of the Milky Way and M31, and more similar to clusters in the Small Magellanic Cloud. The ellipticities do not show any correlation with age or mass, suggesting that rotation is not the main cause of elongation in the M33 clusters. The position angles of the clusters show a bimodality with a strong peak perpendicular to the position angle of the galaxy. These results support the notion that tidal forces are the reason for the cluster flattening. We have fit analytical models to the surface brightness profiles, and derived structural parameters. The overall analysis shows several differences between the structural properties of the M33 cluster system and cluster systems in nearby galaxies. Finally, we have performed a spectroscopic study of star clusters in the above mentioned catalog. We present high-precision velocity measures of 45 star clusters, based on observations from the 10.4m Gran Telescopio Canarias (GTC) using OSIRIS and 4.2m William Herschel Telescope (WHT) using WYFFOS. All the clusters have been previously confirmed using HST imaging, and ages and integrated photometry are known. The velocity of the clusters with respect to local disk motion increases with age for young and intermediate clusters. The mean dispersion velocity for the intermediate age clusters in our sample is significantly larger than in previous studies. Analysis of these velocities along the major axis of the galaxy show no net rotation of the intermediate age subsample. The small number of old clusters in our sample does not allow for any conclusive evidence in that age division.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Izaskun San Roman Aberasturi.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.
Local: Adviser: Sarajedini, Ata.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-11-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0043990:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043990/00001

Material Information

Title: The Formation and Evolution of M33 as Revealed by its Star Clusters
Physical Description: 1 online resource (323 p.)
Language: english
Creator: San Roman Aberasturi, Izaskun
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: clusters -- content -- galaxies -- m33 -- stellar
Astronomy -- Dissertations, Academic -- UF
Genre: Astronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Numerical simulations based on the Lambda-Cold Dark Matter (Lambda-CDM) model predict a scenario consistent with observational evidence in terms of the build-up of Milky Way-like halos. Under this scenario, large disk galaxies derive from the merger and accretion of many smaller subsystems. However, it is less clear how low-mass spiral galaxies fit into this picture. The best way to answer this question is to study the nearest example of a dwarf spiral galaxy, M33. We will use star clusters to understand the structure, kinematics and stellar populations of this galaxy. Star clusters provide a unique and powerful tool for studying the star formation histories of galaxies. In particular, the ages and metallicities of star clusters bear the imprint of the galaxy formation process. We have made use of the star clusters to uncover the formation and evolution of M33. In this dissertation, we have carried out a comprehensive study of the M33 star cluster system, including deep photometry as well as high signal-to-noise spectroscopy. In order to mitigate the significant incompleteness presents in previous catalogs, we have conducted ground-based and space-based photometric surveys of M33 star clusters. Using archival images, we have analyzed 12 fields using the Advanced Camera for Surveys Wide Field Channel onboard the Hubble Space Telescope (ACS/HST) along the major axis of the galaxy. We present integrated photometry and color-magnitude diagrams for 161 star clusters in M33, of which 115 were previously uncataloged. This survey extends the depth of the existing M33 cluster catalogs by ~1 mag. We have expanded our search through a photometric survey in a 1deg x 1deg area centered on M33 using the MegaCam camera on the 3.6m Canada-France-Hawaii Telescope (CFHT). In this work we discuss the photometric properties of the sample, including color-color diagrams of 599 new candidate stellar clusters, and 204 confirmed clusters. Comparisons with models of simple stellar populations suggest a large range of ages some as old as ~10 Gyr. In addition, we find in the color-color diagrams a significant population of very young clusters (< 10 Myr) possessing nebular emission. Analysis of the radial density distribution suggests that the cluster system of M33 has suffered from significant depletion, possibly due to interactions with M31. To further understand the properties of M33 star clusters, we have carried out a morphological study 161 star clusters in M33 using ACS/HST images. We have obtained, for the first time, ellipticities, position angles, and surface brightness profiles of a statistically significant number of clusters. Ellipticities show that, on average, M33 clusters are more flattened than those of the Milky Way and M31, and more similar to clusters in the Small Magellanic Cloud. The ellipticities do not show any correlation with age or mass, suggesting that rotation is not the main cause of elongation in the M33 clusters. The position angles of the clusters show a bimodality with a strong peak perpendicular to the position angle of the galaxy. These results support the notion that tidal forces are the reason for the cluster flattening. We have fit analytical models to the surface brightness profiles, and derived structural parameters. The overall analysis shows several differences between the structural properties of the M33 cluster system and cluster systems in nearby galaxies. Finally, we have performed a spectroscopic study of star clusters in the above mentioned catalog. We present high-precision velocity measures of 45 star clusters, based on observations from the 10.4m Gran Telescopio Canarias (GTC) using OSIRIS and 4.2m William Herschel Telescope (WHT) using WYFFOS. All the clusters have been previously confirmed using HST imaging, and ages and integrated photometry are known. The velocity of the clusters with respect to local disk motion increases with age for young and intermediate clusters. The mean dispersion velocity for the intermediate age clusters in our sample is significantly larger than in previous studies. Analysis of these velocities along the major axis of the galaxy show no net rotation of the intermediate age subsample. The small number of old clusters in our sample does not allow for any conclusive evidence in that age division.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Izaskun San Roman Aberasturi.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.
Local: Adviser: Sarajedini, Ata.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-11-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0043990:00001


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DuringmywholelifeIhavealwaysconsideredmyselfaveryluckypersonforthewonderfulexperiencesandgreatpeoplethatIhavemetalongthejourney.OnceagainhereIamwiththedifculttaskofexpressingmyappreciationtothemany,manypeoplethateitherdirectlyorindirectlyhaveinuencedthisadventureandcontributedtothiswork.Firstofall,Iwouldliketoexpressmysinceregratitudetomyadvisor,Prof.AtaSarajedini,forhiscontinuoussupportpersonallyandprofessionally,forhispatience,motivation,enthusiasm,andimmenseknowledge.Ithasbeenanhonorformetolearnandworkathisside.Withouthisguidance,theselastyearswouldhavebeenacompletelydifferentstory.Icouldnothaveimaginedhavingabettermentorandadvisorformygraduateyears.Thanksalsogotomyresearchgroup,Karen,Maren,Soung-Chul,andRogerfortheinvaluablehelpwithresearch.Iwouldnothavesurvivedtheseyearsifitwerenotformyfellowgraduatestudentsandfriends,andallthefuntimesandlaughterwehaveshared.IthankSun,Curtis,andDanG.forbeingthebestofcematesever.Iwillalwaysrememberthegreat/strangemomentslivedinside,andoutside,ofce315withasmile.Ialreadymissyou.IwouldalsoliketothankDimitriandJesusforthewonderfulconversationsaroundgreatfood.IthankDanC.forsharingthejourneywithme,fromhishelpwithmyEnglishinmyrstyearstothehardtimesattheend.ThanksaswelltotheSpanishcommunityinthedepartmentformakingtheinitialtransitionapieceofcake.SpecialthankstoPaolaandMiguelfortheirgreatfriendship.Iwouldliketothankmyfriends,Mariluz,Ainara,Elena,andVeroforbeingalwaysbeenthereforme,althoughnotphysicallypresent.Iamverygratefulformywonderfulandlovingfamily.Iwouldliketothankmyparents,PiliandBalbino,andmysistersBeatrizandEdurnefortheirunconditionalsupportandforneverquestioninganyofmysometimedifcultdecisions.Thanksforletmedreambig.Inspiteofthedistance,youcouldnotbeclosertome.Finally,Iwould 4

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page ACKNOWLEDGMENTS .................................. 4 LISTOFTABLES ...................................... 8 LISTOFFIGURES ..................................... 9 ABSTRACT ......................................... 11 CHAPTER 1INTRODUCTION ................................... 14 1.1MotivationandRelevance ........................... 14 1.2StarClustersasAstronomicalTools ..................... 15 1.3StarClusterSystemsintheLocalGroupGalaxies ............. 17 1.3.1MilkyWay ................................ 17 1.3.2M31 ................................... 20 1.3.3MagellanicClouds ........................... 22 1.3.4DwarfGalaxiesandBeyond ...................... 23 1.4M33 ....................................... 25 1.4.1OurCurrentKnowlegde ........................ 25 1.4.1.1StellarPopulation ...................... 25 1.4.1.2KinematicsandGasStructure ............... 27 1.4.2ThisStudy ................................ 27 2NEWLYIDENTIFIEDSTARCLUSTERSINM33:SPACE-BASEDSURVEY .. 30 2.1ObservationsandDataReduction ...................... 31 2.2ClusterIdenticationandPhotometry .................... 34 2.2.1ComparisonwithPreviousPhotometry ................ 36 2.2.2ComparisonwithPreviousCatalogs ................. 38 2.3Color-MagnitudeDiagrams .......................... 40 2.4Analysis ..................................... 42 2.5Summary:NewlyIdentiedStarClusters .................. 44 3PHOTOMETRICPROPERTIESOFTHEM33STARCLUSTERSYSTEM:GROUND-BASEDSURVEY ............................ 45 3.1ObservationsandDataReduction ...................... 45 3.2ANewCatalogofStarClusterCandidatesinM33 ............. 47 3.2.1ClusterSearchMethod ......................... 47 3.2.2HighlyProbableClusters ........................ 50 3.3Analysis ..................................... 53 3.3.1Color-MagnitudeDiagrams ...................... 53 3.3.2Color-ColorDiagrams ......................... 54 6

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......................... 58 3.3.4AdditionalComparisonsWithOtherGalaxies ............ 59 3.3.5SpatialDistribution ........................... 65 3.4Summary:PhotometricProperties ...................... 69 4STRUCTURALPARAMETERSOFTHEM33STARCLUSTERSYSTEM ... 70 4.1ObservationsandDataReduction ...................... 71 4.2Ellipticities .................................... 72 4.3SurfaceBrightnessProles .......................... 79 4.3.1IrregularProles ............................ 80 4.3.2ProleFitting:KingvsEFF ...................... 83 4.4StructuralParameters ............................. 87 4.4.1ComparisonwithOtherGalaxies ................... 87 4.4.2GalactocentricDistribution ....................... 90 4.5Summary:StructuralParameters ....................... 91 5KINEMATICPROPERTIESOFSTARCLUSTERSINM33 ........... 94 5.1ObservationsandDataReduction ...................... 95 5.2RadialVelocityMeasurements ........................ 98 5.3Analysis ..................................... 102 5.3.1ComparisonwithPreviousStudies .................. 102 5.3.2VelocityDispersionversusAge .................... 102 5.4Summary:Kinematics ............................. 106 6CONCLUSIONS ................................... 108 6.1Summary .................................... 108 6.2DiscussionandFutureWork ......................... 113 APPENDIX ASPACE-BASEDSTARCLUSTERCATALOG ................... 116 BCOLOR-MAGNITUDEDIAGRAMS ......................... 120 CGROUND-BASEDEXTENDEDSOURCESCATALOG .............. 194 DSTRUCTURALPARAMETERCATALOGS ..................... 248 ESURFACEBRIGHTNESSPROFILES ....................... 269 REFERENCES ....................................... 312 BIOGRAPHICALSKETCH ................................ 322 7

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Table page 2-1ObservationSummary ................................ 32 2-2CrossIdenticationwith Zloczewskietal. ( 2008 ) ................. 39 3-1CrossIdenticationwith Grossietal. ( 2010 ) .................... 58 5-1KinematicPropertiesofM33StarClusters(GTCObservations) ......... 100 5-2KinematicPropertiesofM33StarClusters(WHTObservations) ........ 101 A-1ClusterProperties .................................. 116 C-1ExtendedSourceCatalog .............................. 194 D-1EllipticitiesandPositionAngles ........................... 248 D-2StructuralParametersfromtheKingProleFit .................. 253 D-3StructuralParametersfromtheEFFProleFit .................. 260 8

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Figure page 1-1DistributionofLocalGroupmembers. ....................... 18 1-2A1x1digitizedskysurveyimageofM33 .................... 26 2-1Locationofthe12observedACS/WFC ...................... 32 2-2Newlyidentiedstarclusters ............................ 35 2-3Comparisonwithpreviousstudiesoftheintegratedclusterphotometry ..... 36 2-4Color-magnitudediagramofnewlyidentiedstarclusters ............ 39 2-5Radialcolor-magnitudediagramforcluster7 ................... 42 2-6Variationoftheintegratedcolorsasafunctionofage ............... 43 3-1Illustrationofthesearchmethodadopted ..................... 48 3-2Comparisonoftheintegratedclusterphotometry ................. 49 3-3Sextractorparameterdistribution .......................... 51 3-4Color-magnitudediagramsandcolordistributions ................. 53 3-5Color-colordiagrams ................................. 55 3-6GalexFUVimageofM33andtheveryyoungstarclustercandidates ...... 57 3-7Gapinthecolor-colordiagram ........................... 60 3-8Color-magnitudediagramsofstarclustersindifferentgalaxiesoftheLocalGroup ......................................... 61 3-9Color-colordiagramsofstarclustersindifferentgalaxiesoftheLocalGroup .. 63 3-10Cumulativeradialdistribution ............................ 66 3-11Radialdensitydistribution .............................. 67 4-1Ellipticitiesandpositionanglesasafunctionofsemi-majoraxes ........ 74 4-2Ellipticitiesversusclusterproperties ........................ 75 4-3Meanellipticityofstarclustersasafunctionoftheirhostgalaxyluminosity ... 77 4-4Clusterelongationsandorientations ........................ 78 4-5Distributionofthepositionangles .......................... 79 4-6Surfacebrightnessprolesandmodelts ..................... 81 9

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................... 82 4-8Qualityofthemodelts ............................... 85 4-9Derivedhalf-lightradiiinfromdifferentltersandmodels ............ 86 4-10Comparisonofstructuralparameterswithdifferentnearbygalaxies ....... 88 4-11Structuralparametersasafunctionofage ..................... 89 4-12Half-lighradiusasafunctionofrenormalizedgalactocentricdistance ...... 92 5-1GTC/OSIRISspectra ................................. 99 5-2Velocitycomparisonwithpreviousstudies ..................... 103 5-3ClustervelocitydispersionrespecttheM33diskmotionasafunctionofage .. 105 5-4Radialvelocityoftheclustersasafunctionofdistancefromtheminoraxis .. 106 6-1Illustrationofourground-basedandspace-basedsurveys ............ 111 10

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Navarroetal. 1997 ).Astheprogenitordisrupts,itsstellarcomponentsareincorporatedintothehalo.Therefore,thereisadeepconnectionbetweentheagesandchemicalcompositionsoftheparent-progenitorsystem.Tidaldebrisaredepositedinbothandcanmaintainspatialandkinematiccoherenceformanygigayears( Bullocketal. 2001 ).Accordingly,stellarhalosofgalaxiesunderthiscontextshouldpossesssignicantspatialandmetallicitysubstructureintheformofdisruptedsatellites.WehaveobservationalevidencesupportingthisviewsuchastheSagittarius(Sgr)dwarfspheroidalgalaxy,whichisintheprocessofbeingcannibalizedbytheMW( Ibataetal. 1994 ).EvidenceofdwarfsatellitedisruptionhasalsobeendetectedinothergalaxiessuchasintheM31halo( Fergusonetal. 2002 )andNGC5128( Pengetal. 2002 ).ItislessclearhowaccuratetheCDMframeworkisatlowergalaxymasses.Wheredothelowmassdwarfspiralstintothisparadigm?Whatistherelationbetweendwarfspiralgalaxiesanddwarfspheroidals/irregulars?Shouldweexpectdisrupteddwarfgalaxiesortidaltailsinthevicinityofadwarfspiralgalaxy?Withthesequestionsinmind,wehavestudiedthenearestexampleofadwarfspiralgalaxy,M33.ThisthesisprojectwillshedlightontheCDMparadigmthroughamorecompletepictureofthestarformationhistory,chemicalenrichmentandkinematicsofadifferentmorphologicaltypeofgalaxy. 14

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Galletietal. ( 2004 )),itistheonlynearbylate-typespiralgalaxy,anditprovidesanotableconnectionbetweenthepopulationofearlier-typespiralsandthenumerousnearbylater-typedwarfgalaxies.Withatotalmass20timeslowerthantheMWandonly2timesgreaterthantheMagellanicClouds( Corbelli 2003 ),M33providesauniqueopportunitytotesttheCDMframework'spredictionsinaregimedifferentfromtheMW.Inaddition,thegalaxypresentsanearlyface-onview(56)allowingustostudybothitsdiskandhalopopulations. Ashman&Zepf 1998 ).OCsareverydifferentfromGCs.Theyarelessdenselypopulated,lessmassiveandgenerallyyounger.OCsareconnedtothegalacticplaneandusuallyassociatedwiththespiralarms( Trumpler 1930 ; Friel 1995 ).Thedenitionofastarclusterhasevolvedandextendedastheirpropertieshavebeeninvestigatedindetailandastheyhavebeendiscoveredindifferentextragalacticenvironments.TheLargeMagellanicCloud(LMC)containsclustersresemblingGCsinshapeandpopulationbutwithagessimilartoopenclustersinourgalaxy(e.g. Hodge 1961 ; Kontizasetal. 1987 ; vandenBergh 1991 ).TheseclusterscalledbluepopulousclustershaveintermediatemassesbetweenOCsandGCs.Anotherpeculiartypeofclusterhasbeenfoundinmanymergersandstarburstgalaxies.They 15

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PortegiesZwartetal. 2010 ).ThebluepopulousclustersintheLMCandtheYMCsfoundinmergersandstarburstsareprobablysimilartypesofobjects.Recentinfraredobservationshaveshownthatalthoughrare,theMWalsopossessYMCs( Clarketal. 2005 ). Huxoretal. ( 2005 )reportthreenewclustersdiscoveredinthehaloofM31which,althoughhavingglobular-likecolorsandluminosities,haveunusuallylargesizesandareunlikeanyclustersfoundintheMW.Theseextendedstarclusters(ESC)havealsobeendiscoveredinothergalaxieslikeM33( Stonkuteetal. 2008 ; Cockcroftetal. 2011 )andseemnottobelimitedtospiralgalaxies( DaCostaetal. 2009 ).Thepreciserelationshipbetweenallofthesetypesofobjectsisnotyetclear.Infactithasbeensuggestedthatitisonlyamatterofsemanticsandthebasicmechanismbehindtheformationofalloftheseobjectsisthesame.Ontheotherhand,anincreasingnumberofdetailedphotometricstudiesinGCsisseriouslyquestioningthegeneralviewofstarclustersassinglestellarpopulations.Asplitofdifferentevolutionarysequenceshavebeenobservedinthecolor-magnitudediagramsofmanyGCs.MultiplestellarpopulationshavebeenidentiedinGalacticandMagellanicCloudstarclusters( Piotto 2009 ).Duringthisprojectwewilladoptadeliberatelybroaddenitionoftheterm'starcluster'referingtoanyboundgroupofstars.Inspiteofthechallengesthattheseobjectspresent,andthemanyunresolvedquestions,starclustersarecrucialformanyareasofastrophysics.Forexample,starclustersaretheobservationalfoundationforstellarastrophysicsandevolution.Itisalsowidelyacceptedthatstars,ingeneral,donotforminisolationbutinstarclusters( Lada&Lada 2003 ).Overtime,clustersaredisruptedordestroyedandtheirmembersbecomepartofthegeneraleldpopulation.Atthesametime,starclustersarefound 16

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( 1936 )wasthersttointroducetheideathatourgalaxy,MW,belongstoasmallclusterofgalaxies,theLocalGroup(LG).Thegroupcontainsmorethan50knownmembers,butthisnumberkeepsgrowingasdetectionlimitsreachfaintersurfacebrightnesses.Figure 1-1 showsthedistributionoftheprincipalLGmembersandplacesM33initsneighborhood.ThegureshowsthattheLGisaclusterwithabinarycore.ThemajorityofLGmembersbelongtoeithertheM31subgroup,ortheMWsubgroup,thetwomassivespiralgalaxiesoftheLG.Asmentionedpreviously,M33isthethirdspiralgalaxyintheLGandistheonlynearbyrepresentationofadwarfspiral.ThegalaxiesoftheLGareourclosestextragalacticneighbors,closeenoughtoberesolvedintoindividualstarsandtobestudiedindetail.Thesenearbygalaxiesincludeawidevarietyofmorphologicaltypesandawiderangeofagesandmetallicities.ComparingtheresultsofourstudywithstarclustersystemsinavarietyofenvironmentsisofspecialimportancetounderstandinghowtheM33starclustersystemhasevolved.Forthisreason,wededicatethissectiontodiscuss,briey,thepropertiesofstarclustersystemsintheLGgalaxies. 17

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DistributionoftheprincipalLocalGroupmembers,asviewedfromtwoorthogonaldirections.TheX,YandZaxespointtowardstheGalacticcenter(l=0,b=0),thedirectionofrotation(l=90,b=0)andthenorthGalacticpole(b=+90),respectively.Thecircleofradiusof1180kpccorrespondstothezero-velocitysurfaceoftheLG.Thedashedcirclewithradius450kpcshowstheradiusofthespherethatcontainshalfofallLocalGroupgalaxies.(From vandenBergh ( 1999 )). Asindicatedbytheirname,GCstendtobesphericalandarecharacterizedbyahighcentralstellardensityofanoldpopulation.TheMWhas158GCs( Harris 1996 )andhasbeenstudyindetailed.TheyareamongtheoldestobjectsintheUniverse,providinguswithuniquefossilrecordsoftheearlyevolutionofourGalaxy.TheypopulatethehaloandbulgeoftheMWwithasignicantconcentrationtowardtheGalacticCenter.About50%ofGCsresidewithin5kpcofthecenteroftheGalaxy,althoughtheyarealsofoundasfaras100kpcfromthecenter( Barbuyetal. 1998 ). 18

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Armandroffetal. 1992 ).GCshavetypicalmassesof105Mandmeanhalf-lightradiiofrh3pc.Perhapsthemostdistinguishedfeatureoftheseobjectsisthebimodalityoftheirmetallicitydistribution.Thedistributionshowstwodistinctpeaksat[Fe/H]=.59and[Fe/H]=.51( Ashmanetal. 1994 ; Armandroff&Zinn 1988 ).Themetal-poorclustershaveasphericaldistributionaboutthegalacticcenterwithasmallrotationalvelocityandalargevelocitydispersion.Themoremetal-richclustershavepropertiesofadisksystemwithhighlyfattenedspatialdistribution( Zinn 1985 ).Thesepropertiessuggesttwodistinctsubpopulations:athickdiskorbulgepopulationandahalopopulation( Zinn 1985 ; Armandroff 1989 ).Otherwise,thetwopopulationsofclustersseenindistinguishable(e.g.luminosityfunctions( Armandroff 1993 )).Recentevidencesuggeststhatthehalopopulationmayitselfbeacompositesystem:anoldhalocomponentmorecentrallyconcentratedandwithaverysmallagespread,andayoungerhalopopulationwithasignicantagespread( Zinn 1993 ).TheoldhaloGCsshowsignicantprograderotationwithlowline-ofsightvelocitydispersionwhiletheyoungeroneshaveahighvelocitydispersionandanindicationofretrograderotation.Inaddition, Zinn ( 1993 )notesthattheyounghalopopulationdoesnotshowevidenceofametallicitygradientwithgalactocentricdistancecontrarytothesignicantgradientamongtheoldhalopopulation.Thesedifferentbehaviorssuggestthattheyounghalocomponentmayhavebeenaccretedfromnearbysatellites.Ontheotherhand,OCsareverydifferentfromGCs.OCsareknowntobelessdenselypopulatedandyounger.Morethan1,000openclustershavebeenfoundintheMWandmanymoreareexpectedtobehiddenbehindthedustorthehighlydensebulge.Theyareknowntobeconnedtothediskandhavebeenused,amongotherpurposes,todeterminethespiralarmstructureandtomaptherotationcurveoftheMW. 19

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vandenBergh&McClure 1980 ).Inaddition,theseclustersarealsosignicantlymoremassiveoverlappingwiththeleastmassiveGCs( Kaluzny&Udalski 1992 ; Friel 1995 ).Whileluminosityfunctionsforyoungopenclusterscontinuetoincreasetofaintermagnitudesandlowermasses,strongevidencesuggestthattheluminosityfunctioninolderclusterseitherattenorreachamaximum,turnover,anddecreasetowardfaintermagnitudes( Aparicioetal. 1990 ; Montgomeryetal. 1993 ). McConnachieetal. 2005 ),M31'sproximitypermitsstudiesofindividualresolvedstarsinitsclusters.Howevertheextensionofthegalaxyoverafewdegreesontheskyhasmadesurveyingitsentirepopulationchallenging.Broadlyspeaking,theM31GCsystemisquitesimilartothatofourgalaxy,howeverdetailedstudieshavefoundsomecleardifferences. Barmby&Huchra ( 2001 )estimatethetotalnumberofGCsinM31tobeintherangeof450-500,afactorof2.5greaterthantheMWsystem. Caldwelletal. ( 2009 )presentadetailedstudyofthepropertiesof670likelystarclusters.Theydividethesampleintoyoung(<2Gyrs),intermediate,andoldclusters(>6Gyrs).Youngclusterspresentspatialandkinematicpropertiesconsistentwithformationinthestar-formingdiskofM31.Theclustershavemassesrangingfrom250 20

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Caldwelletal. 2011 ).TheM31haloGCpopulationpossessesnosignicantmetallicitygradient( Alves-Britoetal. 2009 ; Huxoretal. 2011 ).Themetal-richclustersarecentrallyconcentratedwithahighrotationamplitudebutconsistentwithabulgepopulation.Themetal-poorclusterstendtobelessspatiallyconcentrated.TheentireGCsystemshowsstrongrotationandaweakrotationpersistsevenfortheoutermostclusters( Leeetal. 2008 ).TheluminositydistributionsofMWandM31GCsareroughlysimilar( Huxoretal. 2011 )butM31hasapopulationofluminousGCsatlargegalactocentricdistancesthataresignicantlymoreluminousthantheouterhaloGCsintheMW( Galletietal. 2007 ; Huxoretal. 2011 ).TheGChaloofM31isalsoconsiderablylargerinphysicalextentthantheMWhalo,withthemostremotemembercurrentlyknownlyingataradialdistanceof200kpc( Mackeyetal. 2010 ).InadditionM31hostsapopulationofluminousextendedGCswhichcurrentlyhavenoknowncounterpartsintheMW( Huxoretal. 2011 ).AlloftheevidenceprovidessupportforaccretionplayingasignicantroleinbuildinguptheM31GCsystem. Mackeyetal. ( 2010 )showevidencethatthemajorityoftheremoteglobularclustersystemofM31hasbeenassembledasaconsequenceoftheaccretionofcluster-bearingsatellitegalaxies.TheoveralldifferencesinthehaloGCpopulationsoftheMWandM31couldbetheresultofthetwogalaxieshavingexperiencedadifferentnumberofaccretionevents,oraccretionsofadifferenttype.TheMWcouldhaveaccretedmostlylow-masssatelliteswhichcarryfew,ifany,associated 21

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Fardaletal. 2008 ). Mackey&Gilmore 2004 ).ClustersintheLMCpopulatealmostallevolutionaryphasesandoccupyregionsoftheageandmetallicitydomainnotpopulatedintheMWorM31.ThischaracteristichasmadetheLMCclustersystemanidealtargettotestevolutionarymodels.TheLMCclusterpopulationcontainsonly15oldGCs.Therealsoexistsaverysubstantialpopulationofyoungandintermediateageclusters.TheLMCclustersystemshowsapeculiaragedistributionrevealingnoclusterswithagesbetween3Gyrand10Gyr.ThisanomalyiscalledtheLMCclusterage-gap(e.g. Richetal. 2001 ).Onlyoneclusterissuspectedtoliewithintheage-gap,ESO121-SC03.ThisremotenorthernLMCmemberhasbeenstudiedindetail(e.g. Sarajedinietal. 1995 ; Bicaetal. 1998 ).Recentstudieshaveexplainedtheexistenceoftheage-gapbasedontheimpactoftheperiodicstrongtidalinteractionsbetweentheLMC,SMCandMW( Bekkietal. 2004 ).Infact,signaturesoftheseinteractionscanbeseeninHImapsascomplexenvelopesofgasinandaroundtheMagellanicClouds.BothCloudsareconnectedthroughabridgeofmaterial,theMagellanicBridge,thatwaslikelystrippedfromtheSMCinapreviousencounter.Inaddition,theMagellanicStreamtrailstheCloudsintheirorbitaroundtheMWasaresultoftidalstrippingofmaterialfromtheMagellanicCloudsbytheMW( Putmanetal. 2003 ). Schommeretal. ( 1992 )inferredthedistributionoftheLMCclustersandfoundthattheentireclustersystemrotateswithdisk-likekinematics,whilenoclustersappearto 22

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Borissovaetal. ( 2004 )arguetheexistenceofatenuoushaloofmetal-poorRRLyraestars.ThesmallerandlessmassiveSMCcontainsfewerclustersthantheLMCandingeneralhasbeenlesswellstudied.Theclusterformationhistoryandage-metallicityrelationseemstobeverydifferentbetweentheSMCandLMC( DaCosta 2002 ),howevertheSMCcontainsmassivestarclusterssimilartothosefoundintheLMC.TheonlyoldSMCGC,NGC121,is23GyryoungerthantheoldestMWandLMCGCs.Withanabundanceof[Fe/H].45,NGC121isnotnotablymetal-poor( Glattetal. 2008 ).IncontrasttotheLMC,noage-gaphasbeendetectedamongitsclustersandindeed,theSMCpossessesasignicantnumberofclustersbetween410Gyr.ItseemsthattheSMChasformeditsstarclusterscontinuouslytothepresentdayoverthelast7.5Gyr( Glattetal. 2010 ).TheoldestSMCclustershavehigherellipticitesthantheLMCGCsandevenhigherellipticitiesthantheverysphericalMWclusters( Hill&Zaritsky 2006 ). Mateo 1998 ).WehavelongknownthatmanydwarfgalaxieshaveGCsystems.ThepeculiaritiesofthestarclustersystemsinthedIrrsLMCandSMChavealreadybeendiscussedinSection 1.3.3 .ThedIrrNGC6822(MV.2)hasthreeoldGCs,twoofwhicharelocatedfarfromthemainbodyofthegalaxy( Cohen&Blakeslee 1998 ; Hwangetal. 2005 ).ThedIrrWLM(MV.5)hasonlyoneoldGCanditismetal-poor( Hodgeetal. 1999 ).Thelowest-luminosityLGgalaxieswithconrmedGCsarethedSphsFornax(MV=.1)andSagittariusdwarf(MV=.9),eachofwhichhasatleastveGCs(e.g. 23

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, 1981 ; DaCosta&Armandroff 1995 ).SeveralGCsinSgrandCMajareofintermediateageandmetallicity( Zinn 1999 ). Bellazzinietal. ( 2003 )suggestagroupofouterMWhaloGCs(M54,Ter7,Ter8,andArp2)tobeassociatedwiththemainbodyoftheSagittariusdSphgalaxy.PropertiesofNCG1851,1904,2298,and2808alsosuggestthattheseclustershavebeenaccretedfromtheCMajdSphgalaxy( Martinetal. 2004 ).LessisknownabouttheGCsystemsofM31dwarfs,althoughdEsNGC147,NGC185andNGC205areknowntohaveGCsystems.ItisbelievedthatGCsindEsareuniformlymetal-poorwithapeakat[Fe/H].8( Minnitietal. 1996 ). DaCosta&Mould ( 1988 )indicatethatthesesystemsarepredominantlyoldandmetalpoorexceptforoneclusterwithanintermediate-age.Lower-massGalacticdwarfs(e.g.,LeoI; vandenBergh 2000 )donothaveGCs.Insummary,itappearsthatonlythemostluminousLGdwarfgalaxiespossessafewGCswhilethefaintergalaxiescannotproducetheseobjects.TheseobservationscanconstraintstheminimummassofhaloswithinwhichGCscouldform.Althoughobservationallychallenging,starclustershavealsobeendetectedingalaxiesbeyondtheLG.Inthesedistantsystems,clustersappearindistinguishablefromstarsundereventhebestconditions.LargeellipticalsarethemostnaturalenvironmentsforGCsystemsandtheypossessontheorderofthousandsofGCs( Kundu&Whitmore 2001 ).Veryyoungsuperstarclustersoryoungmassiveclustershavebeenfoundinmanystarburstgalaxies.Largepopulationsofyoungstarclustershavealsobeendetectedinmergerscenarios.Thisapparentubiquitymakesstarclusterspowerfultoolsformanyastronomicalpurposes.FurtherdiscussionsaboutstarclustersintheLGandbeyondareincludedin Harris ( 1996 )and Brodie&Strader ( 2006 ) 24

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1.4.1OurCurrentKnowlegdeAtadistanceof870kpc,M33istheonlydwarfspiralgalaxyintheLG( Galletietal. 2004 ).WithatotalvisualmagnitudeofMv.9( vandenBergh 1991 )itisoneofthemostdistantobjectsthatcanbeviewedwiththenakedeye.Figure 1-2 showsa1x1imagecenteredonM33.Thegalaxyhasapositionangleof23andaninclinationofthediskwithrespecttotheplaneoftheskyof56( Regan&Vogel 1994 ).IthasbeendenedasaSc-Sdgalaxyand,likeothergalaxiesinthisclass,doesnotpossessaclassicalbulge( Minnitietal. 1993 ).Itdoesnothaveeitherasupermassiveblackholeinitscenter( Gebhardtetal. 2001 ).M33hasapoorlydenedspiralarmmorphology( Sandage&Humphreys 1980 )butitsarmsareparticularlyrichinstarformingHIIregionsincludingNGC604,thesecondmostluminousHIIregionintheLG( GonzlezDelgado&Prez 2000 ). Sarajedinietal. 2006 ; Yangetal. 2010 ),whichprovidesevidenceofastellarpopulationasoldas10Gyrs.ThestellarpopulationoftheM33haloappearstobequitedifferentthantheoneintheMW(<[Fe/H]>=.6).Photometryofhalostarclustersrevealsameanmetallicityof<[Fe/H]>=.270.11( Sarajedinietal. 1998 2000 )whichisnotasmetal-poorasthehaloglobularsintheMW.Additionally,thehaloclusterpopulationspansalargerrangeofages,57Gyrs( Chandaretal. 2002 ),suggestingaprolongedepochofformationtherebysupportingthefragmentationscenario.Incontrast,thestudiesof McConnachieetal. ( 2004 )and Fergusonetal. ( 2007 )donotrevealanyevidenceoftidaltailsorstreamsintheirimagingsurveys,supportingtheisolatedevolutionofM33.However,detectingthesesubstructuresthroughstellardensityenhancementsbecomes 25

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A1x1digitizedskysurveyimageofM33.Northisupandeastistotheleft. verydifcultwiththeirshallowphotometry.Morerecently,andusingamuchdeeperphotometricsurvey, McConnachieetal. ( 2009 )reportapreviouslyunknownprominentstellarstructuresurroundingM33whichfavorsamorecomplexevolutionofthegalaxy.Regardingthestarformationhistoryoftheeldstars, Barkeretal. ( 2007 )foundapositiveagegradientinthreeAdvancedCameraforSurveys(ACS)eldsjustoutsidethebreakradiusonthesouthernminoraxes.Theseresultssupporttheinside-outgrowthmechanism.Apparentlycontradictoryresultsareshownby Williamsetal. ( 2009 ) 26

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Barkeretal. ( 2011 )provideevidenceofanagegradientthatreverseatlargeradiinearthebreakradius. ( 2002 )presentakinematicstudyof107starclustersthatrevealtwodifferentpopulations:youngobjects(<1.3x108yrs)withdisk-likerotationandolderobjects(>8x108yrs)showingverylittleifanyrotation.Incontrast,amongtheeldstars, McConnachieetal. ( 2006 )identifythreevelocitycomponents,disk,haloandathirdfeaturewithavelocitydispersionthatisnotwellconstrained.Theyattributethisthirdcomponenttoapossiblestellarstream.Astudywithadequatevelocityprecisionisneededtoidentifyandfurthercharacterizethisthirdvelocitycomponent.ThespatialdistributionofM33gasseemstobedisturbed.TheouterHIdiskofthegalaxyiswarpedpresentinganS-shapedmorphology( Corbellietal. 1989 ).Althoughitsoriginisstillnotclear,previousstudieshavesuggestedthatitistheresultofaninteractionwithM31( Corbelli&Schneider 1997 ; Bekki 2008 ).ThearmsoftheHIemissionareintheoppositedirectiontothediskrotation,suggestinganencounterintheoppositedirectionofM33diskrotation. Grossietal. ( 2008 )ndapopulationofhighvelocityHIcloudsintheouterregionsofM33thatappeartobedistributedalongthemajoraxisoftheHIdisktowardsthedirectionofM31.ThisfeaturecouldbeevidenceofeitheratidalinteractionwithM31ortheaccretionofadwarfcompanion.

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2 ,wepresentintegratedphotometryandcolor-magnitudediagramsfortheentiresampleandinvestigatethepropertiesoftheseclusters.ThissurveyincreasesthemostupdatedM33catalogofconrmedstarclustersbymorethan40%.ThisworkhasbeenpublishedintheAstrophysicalJournal( SanRomanetal. 2009 ).WhileHSTanditsseveralinstrumentshavebeensuccessfullyusedinthesearchforstarclusters,thesmalleldofviewpermitssurveysonlyoveralimitedregionofthegalaxy.Forthisreasonwehaveexpandedourphotometricsurveyovera1x1areacenteredonM33usingtheMegaCamcameraonthe3.6mCanada-France-HawaiiTelescope(CFHT).Chapter 3 presentstheresultantcatalogthatincludes599newcandidatestellarclustersand204previouslyconrmedclusters.Wepresentu'g'r'i'z'integratedphotometryanddeterminedthefullwidthathalfmaximum,ellipticity,andstellarityoftheextendedsources.Thiscatalogcontainsthedeepestandwidest-eldground-basedphotometryoftheM33starclustersystemto-dateandhasbeenpublishedintheAstrophysicalJournal( SanRomanetal. 2010 ).b)Amorphologicalstudyof161starclustersinM33Thespatialstructuresofstarclustersbeartheimprintoftheirinitialconditionsandtheirdynamicalevolution.Thisrelationunderscorestheimportanceofanalyzingthestructureofindividualclustersinordertounderstandtheformationandevolutionprocessoftheseobjects.InChapter 4 ,wepresentamorphologicalstudyofthe161starclustersinvestigatedin SanRomanetal. ( 2009 ).Wehaveobtained,forthersttime,ellipticities,positionangles,andsurfacebrightnessprolesofasignicantnumber 28

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4 havebeensubmittedforpublicationintheMonthlyNoticesoftheRoyalAstronomicalSocietyinMarch2012( SanRomanetal. 2012 ,submitted)c)Aspectroscopicstudyof45starclustersinM33PositionsandmagnitudesofstarclustersarenotsufcientbythemselvestocharacterizethepropertiesofM33.Informationonthegalaxy'skinematicsandchemicalcompositionisalsorequired.Therefore,wehaveperformedaspectroscopicstudyofstarclustersintheaforementionedM33catalog.WeareinterestedinusingspectroscopicdatatoidentifykinematiccomponentsinM33suchasthedisk,halo,andpotentiallystellarstreams.Toaccomplishthistaskwehavedividedourobservingplanintotwoparts:onepartusingtheWilliamHerschelTelescope(WHT)focusingonthebrightestclusters,andasecondpartusingtheGranTelescopiodeCanarias(GTC)coveringthefainterendoftheluminosityfunction.Inchapter 5 ,wepresentapreliminaryanalysisofthederivedradialvelocities.Finally,inChapter 6 weprovideasummaryofthemostimportantresultsthathavecomeoutofthisdissertation,andtheknowledgethatwehavegainedontheformationandevolutionofM33anditsstarclusterssystem. 29

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Hiltner ( 1960 )presentphotometryof23M33clustercandidatesand23M31globularclustersusingphotographicplatesatthe2.5mMt.WilsonTelescope.Sincethisearlystudy,itwasestablishedthat,ingeneral,clustersinM33arebluerandfainterthanthoseinM31.TherehavebeenanumberofM33clustercatalogspublishedsincethispioneerwork.ThemostcomprehensivecatalogofextendedobjectsinM33wascompiledby Christian&Schommer ( 1982 1988 ).Theypresentacatalogof250nonstellarobjectsincludingphotometryof106starclustercandidates.Morerecently, Mochejskaetal. ( 1998 )detect51starclusterscandidates,ofwhich32werenotpreviouslycataloged.WiththearrivaloftheHST,studiesoftheM33starclustershaverapidlyincreased( Chandaretal. 1999a b c 2001 2002 ; Bedinetal. 2005 ). Maetal. ( 2001 2002c a b 2004a b )obtainedagesofM33starclustersusingspectralenergydistributionsin13intermediateltersoftheBeijing-Arizona-Taiwan-Connecticut(BATC)photometricsystem.Thereaderisreferredtotheworkof Sarajedini&Mancone ( 2007 )(hereafterSM),whichmergedallofthemoderncatalogscompiledbefore2007,forasummaryofthepropertiesofallofthesecatalogs.Eventheresultsof Park&Lee ( 2007 ),whichappearedafterthepublicationofSMhavebeenincorporatedintotheweb-basedversionoftheSMcatalog Zloczewskietal. ( 2008 ,hereafterZKH),whichpresentsacatalogof4780extendedsourcesina1squaredegreeregionaroundM33including3554newcandidatestellarclusters.Forthepurposeofthepresentproject,itisimportanttotakespecialnoteofthetwoclustercatalogsby Chandaretal. ( 1999a 2001 ,hereafter

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Sarajedinietal. ( 2006 )becausewewilladoptsimilarreductionandanalysistechniquesasthesepreviousstudies.Ingeneral,ground-basedimagingcannotclearlydistinguishastarclusterfromanothertypeofextendedsource(e.g.nebula,galaxy),butHubbleSpaceTelescope(HST)imagingwiththeWide-FieldPlanetaryCamera2(WFPC2)ortheAdvancedCameraforSurveys(ACS)providesthespatialresolutionnecessarytoprovideanunequivocaldetermination.Itisforthisreasonthatwehaveundertakenthepresentstudy.Inaddition,andjustasimportantly,theHSTobservationsallowustoconstructcolor-magnitudediagrams(CMDs)ofthestarclusters,whichcanbeusedtoestimateagesandinvestigateanycorrelationsthatmightexistbetweenclusteragesandintegratedphotometricpropertiesaswellasallowingustodeterminestarclustermasses.Section 2.1 describestheobservationsanddatareduction,andSection 2.2 discussestheidenticationandintegratedmagnitudesoftheclusters.Section 2.2.2 includesastatisticalanalysisofthemostrecentprevioussurveyofM33clustersby Zloczewskietal. ( 2008 ).TheanalysisoftheCMDsispresentedinSection 2.3 whileananalysisofthestarclusterpropertiesisinSection 2.4 .Lastly,Section 2.5 presentsourconclusions. 2-1 showsthelocationsoftheseelds.Wehavethreeltersfortheprimaryobservations(F475W,F606W,F814W) 31

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LocationofourobservedACS/WFCeldsoverplottedonanimageofM33.Northisupandeastistotheleft. andtwoltersfortheparallelimages(F606W,F814W).Table 2-1 presentsasummaryoftheobservations. FieldR.A.(J2000.0)Decl.(J2000.0)FilterExp.Time(s) D1013349.89+303548.12F606W22480,11300,1120F814W22480,11522,1142F475W3700D2013339.69+302859.98F606W82480,11300,1120F814W102480,11500,1120F475W3700D3013320.49+302214.99F606W82480,11300,1120F814W102480,11500,1120F475W3700D4013307.89+301506.98F606W82480,11300,1120F814W102480,11500,1120

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FieldR.A.(J2000.0)Decl.(J2000.0)FilterExp.Time(s) F475W3700F1013340.32+303839.89F606W12160F814W12160F2013327.52+303915.42F606W12400F814W12500F3013400.23+303256.43F606W12400F814W12500F4013326.04+303037.64F606W12160F814W12160F5013411.78+302721.94F606W12160F814W12160F6013305.39+302711.88F606W12400F814W12500F7013313.43+302329.64F606W12160F814W12160F8013332.92+301732.37F606W12400F814W12400 2-1 ),whichwereusedforthepointsourcephotometry,wererstmultipliedbythegeometriccorrectionimagetocorrectforthefactthateachACSpixelsubtendsadifferentangleonthesky.Then,thedataqualityleswereappliedbysettingthevaluesofbadpixelstoalargenegativenumbersothatthephotometrysoftwarewillignorethem.ThephotometrywasperformedusingtheDAOPHOT/ALLSTARandALLFRAMEroutines( Stetson 1994 )followingthesameprocedureasthatusedby Sarajedinietal. ( 2000 ).Adetaileddescriptionofhowthepointspreadfunctions(PSFs)wereconstructedhasbeenpresentedin Sarajedinietal. ( 2006 ).ThecorrespondingframesintheF606WandF814Wlterswerematchedtoobtainmeaninstrumentalmagnitudesofcommonstarswhichwerethenmatchedtoformcolors.Thephotometryhasbeencorrectedforthechargetransferefciency(CTE)problemthatACSsuffersusingtheprescriptionof Riess 33

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( 2004 ).Inaddition,thetheoreticaltransformationof Siriannietal. ( 2005 )wasusedinordertoconvertthemagnitudestotheground-basedJohnson-Cousinssystem.Thepipeline-processeddrizzled(`DRZ')imageswereusedfortheintegratedclusterphotometryandweresimilarlyobtainedfromtheHSTarchive.Ineldswheremultipledrizzledimageswereproducedbythepipeline,wederivedpositionaloffsetsbetweentheseframesusingtheimshiftandimcombinetasksinIRAFtoallowustoproduceonemasterimageperlterpereld.Thedrizzlingprocessremovestheskybackgroundandcorrectsthecountstoanexposuretimeofonesecond.Asaresult,tomakethecalculationofphotometricerrorsmorestraightforward,eachDRZimagewasmultipliedbytheexposuretimeandthebackgroundskyvaluewasaddedbackbeforeperformingphotometryontheseframes.Theresultantimageswerethenusedinthederivationoftheintegratedclusterphotometry. Sarajedinietal. ( 2006 )).Figure 2-2 showssampleimagesofsomeofthe161clustersidentiedinthisstudy.Theclusterpositionshavebeendeterminedbyconvolvingeachimagewithanellipticalgaussianof=10pixels.Thiskernelsizewaschosensothattheconvolutionprocesswouldyieldasmoothclusterprolethatisconducivetothenextstep,whichistheapplicationoftheIRAFimexaminetask.Thisroutinewasappliedtothesmoothedclusterprolestodeterminetheclustercenters.TheoptimumpixelcoordinatepositionsweretransformedtorightascensionanddeclinationusingtheWorldCoordinateSystemintheimageheaders.BasedontheworkofSM,whichcomparedthepositionalaccuracyofseveralcatalogswiththosedeterminedusingtheLocalGroupSurveyimagesof Masseyetal. ( 2006 ),weestimateaninternalprecisionofapproximately 34

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RepresentativesampleofstarclusterspresentinoureldsintheF606Wlter.Eachimageisshownwiththesamegray-scaleintensityand5arseconaside,withnorthupandeasttotheleft. Stetson 1987 ).Tobeconsistentwiththepreviousworkof Sarajedinietal. ( 2006 ),wehaveadoptedanapertureradiusof2.2forthemagnitudemeasurementsand1.5"forthecolors.NotethatCBFusedthesameaperturesizefortheirmagnitudesbutavariableaperturerangingfrom1.0"to2.2"withinwhichtomeasureclustercolors.LikeintheCBFstudy,thebackgroundskyisalwaysdeterminedinanannuluswithaninnerradiusof3.5andanouterradiusof5.0.Onceagain,thesemagnitudeshavebeencorrectedforCTEbasedon Riess&Mack ( 2004 )andcalibratedtotheground-basedsystemusingthesynthetictransformationsof Siriannietal. ( 2005 ).Table A-1 inAppendix A detailsthepositionofeachclusteraswellasitsVmagnitude,BVcolor,VIcolor,reddening,age,massandalso,ifapplicable,thealternativeidenticationin Sarajedini&Mancone ( 2007 ).Wecouldnotdeterminethe 35

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ComparisonoftheintegratedclusterphotometryfromthepresentstudywiththatofCBFand Maetal. ( 2001 2002c a ) integratedmagnitudesfortwooftheclustersbecauseoftheirlocationneartheedgeoftheeld.Theformalrandomerrorsonthemagnitudesandcolorsarealllessthan0.01magbecauseofthehighsignal-to-noiseratiooftheseclusters.Clustercandidatesnumber139and59inthecatalogof Sarajedini&Mancone ( 2007 )havebeenrejectedasclustersinthisstudybasedonvisualinspection. Maetal. ( 2001 2002c a ),wearriveatadifferenceofhV(Us-Ma)i=0.040.05,wheretheuncertaintiesarestandarderrorsofthemean.Asweshallseebelow,thesephotometricdifferencesarenotunexpectedforintegratedphotometryofextendedobjectssuchasstarclusters(seealsoTable2of Sarajedini&Mancone ( 2007 )).Figure 2-3 showstheoffsetinmagnitudeandcolorinbothcases.TheintegratedBmagnitudesarenotplottedduetoalackofsignicantnumbersofclusterswithwhichtocompare. 36

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Sarajedini&Mancone ( 2007 )catalog,whicharemeasuredfromground-basedimagestakenfromtheLocalGroupSurveyusingtheMOSAICinstrumentaswellasfromtheworkofCBF.Again,wendnosignicantdifferenceinthemagnitudesandcolorsoftheclusterswehavemeasured.Afurthercheckofourphotometryisprovidedbytherealizationthat,asshowninFigure 2-1 ,severalofoureldsexhibitsignicantoverlap.Thereare10clustersthathavemultiplemeasurementsoftheirmagnitudesandcolors:onecommoncluster 37

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Sarajedini&Mancone ( 2007 ).Figure 2-4 showstheintegratedmagnitudeCMDforallofthegenuineclustersintheSMcatalog.Weseethattheclustersspanamagnituderangeof16V20,whichcorrespondstoMV,usingouradopteddistancemodulusof(mM)0=24.69( Galletietal. 2004 ).Figure 2-4 alsoillustratesthelocationsoftheclustersidentiedinthepresentstudy.ThisnewsampleextendstoMV,whichis1magfainterthantheleastluminousclustersintheSMcatalog,closertothefaintestclustersintheLargeMagellanicCloud( Sarajedini&Mancone 2007 ).Wecanalsocompareourclustercatalogwiththemostrecentcatalogproducedby Zloczewskietal. ( 2008 ,hereafterZKH);theypresentaphotometricsurveyforstellarclustersinM33basedondeepground-basedimagesobtainedwiththeMegaCaminstrumentontheCanada-France-Hawaiitelescope,andtheirclassicationsarebasedonvisualinspectionoftheimages.Theircatalogcontains4780extendedsourcesin 38

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Color-magnitudediagramofthegenuineM33clustersfromtheSMcatalog(opencircles)ascomparedwiththosefromthepresentstudy(lledcircles).ThedistributionofthetwotypesofpointsislargelysimilarexceptthatthepresentcatalogcontainsmorefaintstarclustersthanthatofSM.ThefaintestclustersherehaveMV.0rivalingthefaintestglobularclustersintheMilkyWayandpopulousclustersintheLMC. aregionapproximately1x1.Amongthese,thereare3554newcandidatestellarclustersofwhich122arerelativelybright,likelyglobularclusters.Sixtyofthe3554objectsarepresentinourHST/ACSelds.TheZKHcatalogsuggeststhat51ofthesearenewcandidatestellarclusters;howeverourstudyshowsthatonly21objectsresolveintostarsandthereforeappeartobeclusters.SomeoftheotherobjectsthatZKHconsidertobeextendedturnouttobeclosegroupingsoftwoorthreestars.Othersappeartobebackgroundgalaxiesordiffusenebulae.Table 2-2 providesacross-identicationofthe21commonobjectsthataregenuineclusters.If 39

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Zloczewskietal. ( 2008 ) ID(ZKH)ID(us)R.A.(J2000.0)Decl.(J2000.0)NotesTypea Note.UnitsofRAarehours,minutes,andseconds,andunitsofDecaredegrees,arcminutes,andarcseconds.aProposedclassicationinZKH:-1galaxy,0unclassied,1likelystellarclusterand2analreadyknownhighcondenceclusterincludedin Sarajedini&Mancone ( 2007 )

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2-5 showstheradialCMDandthebestt-isochroneforcluster7asanexampleoftheprocedurewefollowed.Appendix B includesanalogousguresforalltheclustersinoursample.Thetop-lefttothebottom-rightintheleftpanelcorrespondtostarswithin1oftheclustercenter,between1and2,2and3andnallybetween3and4.Thesolidlinesrepresenttheoreticalisochronesfrom Girardietal. ( 2000 )foragesof108,109and1010yrswithametallicityofZ=0.004.Thismetalabundancehasbeenchosenasarepresentativemeanofthediskabundancegradientbasedontheworkof Kimetal. ( 2002 ,seealso Sarajedinietal. ( 2006 )).However,wepointoutthatforagesyoungerthan1Gyr,thereisverylittlesensitivityoftheisochrone-derivedageontheassumedmetalabundance.Theisochroneshavebeenshiftedbyadistancemodulusof(mM)0=24.69( Galletietal. 2004 )andaline-of-sightreddeningvalueofE(V-I)=0.06( Sarajedinietal. 2000 ).Then,weoverplottheisochronesintheobservedCMDslookingforthebestttothemainsequenceturnoff(MSTO)region.Basedon Cardellietal. ( 1989 ),weadoptthefollowingrelationbetweentheextinctionandthereddening:AV=1.3E(VI).Theleftpanelillustratesthegradualdecreaseinclusterstarsatincreasingdistancefromtheclustercenter.Consequently,CMDswithin1oftheclustercenterdisplayasignicantfractionofstarsbelongingtotheclusterrevealingfeaturestoestimateages,whilethelowerpanelshavebeenusedtomonitornon-clusterstars.Rightpanelineachgureshowsthebestt-isochroneforstarswithin1"oftheclustercenter.Inthisway,theagesof148starclustershavebeenestimatedfromacomparisonofthemain-sequenceturnoffphotometrywiththeoreticalisochrones.Insomecases,anadditionalreddeningadjustmentwasneededinordertoalignthemainsequenceof 41

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Girardietal. ( 2000 )foragesof108,109and1010yrandametallicityofZ=0.004.RightPanel:Thebestt-isochroneforstarswithin1"oftheclustercenter. theisochroneswiththedata.Inseveralinstances,themainsequenceandtheturnoffarenotsatisfactorilydenedtopermitacomparisonwithisochrones.Weestimateaprecisionintheisochrone-ttingagesof0.05dexbasedonneighboringisochrones(inage)thatcouldalsopotentiallytthedata.Inthecaseofclusters12,15,18and111,theisochronetisnotaswellestablishedandtheprecisionoftheagereaches0.1dex.Theprecisionofthereddeningsisapproximately0.05mag.TheagesandreddeningsobtainedduringthisprocessarelistedinTable A-1 2-6 showsthevariationofintegratedclusterV-I 42

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Thetoppanelshowsthevariationoftheclusters'integrated(VI)0colorswithage.Thecorrectionforreddeninghasbeeneffectedusingthereddeningvaluesobtainedintheisochronesttingprocess.Thelinesrepresenttheexpectedrelationsforasimplestellarpopulationfrom Girardietal. ( 2002 )withZ=0.004(solidline),Z=0.001(dottedline)andZ=0.019(dashedline).Thelowerpanelshowstheextinctioncorrectedabsolutemagnitudeasafunctionofclusterage.Thedashedlinesaretheexpectedrelationsforasimplestellarpopulationfrom Girardietal. ( 2002 )withZ=0.004andmassesof103,104,105and106M. colorwiththeestimatedisochroneage.ThesehavebeenreddeningcorrectedusingthereddeninglistedinTable A-1 .Thelinesaretheexpectedrelationsaccordingtosimplestellarpopulations Girardietal. ( 2002 )withZ=0.004(solidline),Z=0.001(dottedline)andZ=0.019(dashedline).Asexpected,thisplotrevealsapositivecorrelationbetweenclusterageandVIcolorinmuchthesamemannerasthemodelspredict.Ourdataallowustocomparetheluminositiesoftheclusterswiththeiragesinordertoderivetheclustermasses.ThebottompanelofFigure 2-6 showstheintegratedabsolutemagnitudesasafunctionoftheestimatedisochroneages.ThesehavebeencorrectedusinganextinctionbasedonthereddeninglistedinTable A-1 .Thedashed 43

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Girardietal. ( 2002 )formassesof103,104,105and106MMandassumingaSalpeterinitialmassfunction(IMF).Thisdiagramindicatesthattheclustersinoursampleareconsistentwiththetheoreticalpredictionsofsimplestellarpopulationfadingmodels.Additionally,themajorityoftheclustershavemassesbetween5103and5104M.Theseestimatedmasseswouldnotchangesignicantlyifweweretoassumeotherpower-lawIMFsinconstructingthefadinglines( Tantalo 2005 )althoughweshouldconsiderthemasupperlimitsinothercaseslikeexponentialIMFs( Chabrier 2001 )binary-correctedIMFs( Kroupa 1998 ).Itshouldbenotedthatthedearthofclustersolderthan109yearsisattributabletothefactthatourCMDsaregenerallynotdeepenoughtodetectthemainsequenceturnoffsofclustersolderthanthislimit. Sarajedini&Mancone ( 2007 ).Color-magnitudediagramsofeachclusterhavebeenconstructedinordertodetermineagesviaisochronetting.SimplestellarpopulationmodelsreproducethebehavioroftheclusterageswithdereddenedVIcoloraswellaswithabsolutemagnitude.WehaveincorporatedthesenewclustersintotheexistingcatalogofM33clustersestablishedby Sarajedini&Mancone ( 2007 )increasingbymorethan40%thesetofconrmedstarclustersinthisgalaxy. 44

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2 ( SanRomanetal. 2009 ),theZKHcataloghaslargelyoverestimatedthenumberofclusters,duetoapossiblesystematicmisidentication,whereonlyaround40%ofthe3554proposedcandidatesarelikelytobeactualstellarclusters.Forthesereasonswehaveundertakenthepresentstudy.Thischapterisorganizedasfollows:Section 3.1 describestheobservationsanddatareductionwhilesection 3.2 discussestheadoptedsearchmethodandtheintegratedphotometryoftheclusters.TheanalysisofthephotometricpropertiesandcomparisonwithothergalaxiesareinSection 3.3 .Finally,Section 3.4 presentsasummary. Hartmanetal. 2006 ).TheimagesweretakenusingtheMegaCam/MegaPrimewide-eldmosaicimagerwhichcontains36individualCCDsthatcombinetooffernearlyafull1x1eldofviewwithahighangularresolutionof0.187pixel1.MegaCamoperateswithasetofg'r'i'z'ltersverysimilartothoseoftheSloanDigitalSkySurvey(SDSS)butaslightlydifferentUVltercalledu.Thislterwasdesignedtomaximizethecapabilitiesoftheinstrumentsatshortwavelengthsanditseffectivewavelengthis200redderthantheu'standardlter.Allthearchivalimageswerepre-processedbytheCFHT'sElixirproject.This 45

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Bertinetal. 2002 ,fordetails).Eachnalcombinedmasterimagewasdividedintotwosub-elds,includinganoverlappingarea,todealwiththespatialvariabilityofthePSF.TheimagesofM33areextremelycrowdedmakingtheconstructionofpoint-spreadfunctionsquitechallenging.Inordertoperformaccuratestandardprole-ttingphotometry,weusedDAOPHOT/ALLSTARroutines( Stetson 1994 )inaniterativeway.Firstwefoundallofthestarsoneachimageandproducedsmall-aperturephotometryforthem.WethenusedtheDAOPHOT/PICKroutinetoselectasetof1000reasonablecandidatestobeusedasPSFstars.Afterdeletingthosewithbadpixelsnearby,wesubtractedthestarswithsurroundingneighborstohelpisolatethePSFstars.Theresultinglistofmorethan500stars,inallcases,wasusedtocreateaPSFforeachoftheimages.TheshapeofthePSFwasmadetovaryquadraticallywithpositionontheframe.ToimprovethePSF,wecreatedanimagewherealltheneighborsandstarsthatdonotttherstPSFweresubtracted,obtaininganimprovedsecond-generationPSFoverthissubtractedimage.Appropriateaperturecorrectionwerecalculatedfromisolatedunsaturatedbrightstarswithphotometricerrorssmallerthan0.01mag.Sincethecorrectionvarieswithradiusfromthecenteroftheimages,apolynomialtwas 46

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Hartmanetal. ( 2006 ),thephotometriccalibrationprovidedbytheElixirpipelinewasappliedusingthezero-pointvalues.Inadditionandtodealwiththedifferencesbetweenuandu',weappliedtheequationsfrom Clemetal. ( 2008 )totransformthephotometryfromug'r'i'z'tou'g'r'i'z'.TheintegratedmagnitudesandcolorsforeachcandidateclusterhavebeencalculatedusingtheaperturephotometryroutinesinDAOPHOT( Stetson 1987 ).Tobeconsistentwithpreviousauthors( SanRomanetal. 2009 ; Sarajedinietal. 2007 ; Chandaretal. 1999a 2001 ),wehaveadoptedanapertureradiusof2.2forthemagnitudemeasurementsand1.5forthecolors.Thebackgroundskyisalwaysdeterminedinanannuluswithaninnerradiusof3.5andanouterradiusof5.0.Noaperturecorrectionshavebeenappliedtotheextendedobjects,suchasthestarclustercandidates.Onceagain,thesemagnitudeshavebeenphotometricallycalibratedtotheSDSSstandardsystem.Toderiveaccuratepositionsoftheclustersandtoestimatepropertiessuchasellipticityorfullwidthathalfmaximum(FWHM),wehaveappliedtheSextractorv2.5.0( Bertin&Arnouts 1996 )imageclassicationalgorithm. 3.2.1ClusterSearchMethodOurdetectionmethodisbasedonthefactthatatthedistanceofM33,non-stellarobjectsareexpectedtobemoreextendedthanthePSF.AftersubtractingthestellarPSFfromallofthesourcesinourframes,extendedobjectsleaveadoughnut-shapedappearance,astheyareunder-subtractedinthewingsandover-subtractedinthecenter.WehaveusedDAOPHOT/ALLSTAR( Stetson 1994 )toproduceresidualimagesfreeofallPSFsources.Wehavetrainedoureyestorecognizetheresidualpatternofcandidateclusters.Whilemostbackgroundgalaxiesshoweitheraspiralarmstructureoranelongatedpattern,thecandidatestellarclustersshowsomelevelofassembly. 47

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Illustrationofthesearchmethodadopted.FirstcolumncorrespondstotheoriginalimageswhilethesecondcolumncorrespondstotheresidualimagesafterPSFsubtraction.Rowsfromtoptobottomshow:abackgroundgalaxy,aconrmedstarcluster,andtwonewcandidateclusters.Eachimageisshownwiththesamegray-scaleintensityand15onaside,withnorthupandeasttotheleft. Asanillustration,Figure 3-1 showsoriginalandresidualimagesofdifferenttypesofextendedobjects.Aftervisualinspectionoftheresidualimagesaswellasanalysisoftheoriginalones,thistechniqueleavesuswithatotalof2,990extendedobjects:803candidateclusters,1,969galaxiesand218unknownobjects.Fromthetotalnumberofcandidateclusters,204werepreviouslyidentiedclustersintheSMupdatedwebsiteandconsideredconrmedclustersbasedonHSTandhigh-resolutionground-basedimaging. 48

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Comparisonoftheintegratedclusterphotometryfromthepresentstudywiththecommonobjectsfrom Zloczewskietal. ( 2008 ). The12ACS/HSTeldsexaminedin SanRomanetal. ( 2009 )included72ofthecandidateclustersinthepresentcatalog,where51turnedouttobegenuinestarclusters.Thissuggeststhataround70%oftheproposedcandidateswillbeactualstellarclusters.However,fromthe349guaranteedclusterslistedintheupdatedSM,ourcatalogonlyrecovers204objectsimplyingmissingobjectsmostlyinthecenterofthegalaxy,notsurprisingsincethemethodislesseffectiveinextremelycrowdedregions.ComparisonwiththesimilarstudyofZKHrevealsunexpecteddiscrepancies.Fromthetotal1,752commonobjectsbetweenbothcatalogs,only124sourceswereclassied 49

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SanRomanetal. ( 2009 )argue,thetotalnumberof'true'clustercandidatesintheZKHcatalogisnotlikelytobelargerthan40%.ThissuggestsasystematicmisidenticationinthecandidateobjectpatternoradefectivePSFsubtraction.Figure 3-2 showsthephotometricdifferencesbetweenthetwostudies.Wendameandifferenceof=0.150.02,=0.100.02and=0.040.03whiletheoffsetsforthecolorsare<(g-r)>=0.0180.012and<(r-i)>=0.0370.030.Thedisagreementinthemagnitudeoffsetsdisappearsinthecoloroffsets,whichindicatesthatthephotometricvariationcorrespondstothedifferentadoptedaperturesineachstudy.Thesephotometricdifferencesarenotunexpectedforintegratedphotometryofextendedobjectssuchasstarclusters( SanRomanetal. 2009 ). 3-3 showsthedistributionofthethreeSextractorparameters.ThestellarityparameterobjectclassicationofSextractorallowustoexamineourvisualobjectclassicationwithamoresystematicalgorithm.Basedonitsdenition,astellarityof1correspondstoapointsource(star)andastellarityof0toaresolvedobject(galaxy).ConsideringthepixelscaleoftheCCD(0.187"pixel1),atypicalseeingof0.7andthedistanceofM33(870kpc),ameanclustersizeof4pcwillappearinourimagesasapointsourceobjectof0.9"implyingstellaritiesaround1.Thedistributionofellipticitiespeaksbetweene=0.05-0.2withanextendedtailreaching0.5inbothsamples.Panelb)showsthenormalizedFWHMassumingameanseeingof0.7.TheFWHMofoursamplehastwopeaks:atFWHM1.5thatagreeswiththeconrmedclusterdistributionandanotherpeakatFWHM1.1notassociated 50

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Sextractorparameterdistributionsofthe599newcandidateclusters(opencircles)andthe204previouslyconrmedclustersinthecatalogofSM(lledcircles).Theopenhistogramscorrespondtothedistributionofconrmedclusterswhilethelledhistogramscorrespondtooursampleofcandidateclusters.Thelledareainpaneld)showstheselectedsampleofhighlyprobableclusters. 51

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3-3 c)showsthatthedistributionofstellarityfortheconrmedclustershasastrongpeakat1withaweakpeak<0.2.ThisdistributionofstellaritiessuggeststhatasignicantnumberofconrmedstarclusterswillbemissinginthecatalogifourmainsourceofclassicationweretheSextractorclassicationalgorithm.Althoughthestellarityisaveryusefuldetectionparametertodistinguishbetweenpointsourcesandnon-pointsources,thepossibilityofextendedorpartiallyresolvedclustersinourimages,meansthatthestellarityparametermustbeusedcautiously.Basedonthepropertiesoftheconrmedstarclusters,weselectedasampleofhighlyprobableclustersthatsatisfythefollowingcriteria:a)Ellipticity<0.4;b)1.10.6.WeshowinFigure 3-3 d)thecorrelationbetweenFWHMandellipticitywherethelledareacorrespondstothespeciedselectioncriteria.AminimumconditionhasbeenappliedtotheFWHMinordertoavoidstellarcontaminationorsmallassociations.Noinformationoncolorormagnitudewasusedforselectingthecandidates.Thissub-sampleofhighlyprobableclusterscontains246objectsandhasbeendesignatedasclass2.Analysisofthecontaminationofthissubsampleusingasimilartechniqueasabovesuggeststhat85%ofhighlyprobableclusterswillbegenuinestellarclusters.Table C-1 inAppendix C showsthecompleteextendedsourcecatalogwherethelastcolumncorrespondstoourproposedclassicationoftheobjects:1=galaxy,0=unknownextendedobject,1=candidatestarcluster,2=highlyprobableclusterand3=conrmedclusterbasedontheSMcatalog.Basedonthisclassication,thecatalogcontains599newcandidateclusters(353candidateclusters(class1)and246highlyprobableclusters(class2)).ThesampleofhighlyprobableclustersaswellastheguaranteedclustersinSMwillbeusedastargetsforfuturefollow-upobservations. 52

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Color-magnitudediagramsandcolordistributionsofthenewstarclustercandidates(opencircles/unlledhistogram)ascomparedwithconrmedclustersfromSM(lledcircles/lledhistogram). 3.3.1Color-MagnitudeDiagramsIntrinsicpropertiessuchasage,metallicity,andreddeninggoverntheintegratedmagnitudesandcolorsofclusters.Asdescribedintheprevioussections,wehaveperformedaperturephotometryofthecandidate(class1and2)andconrmed(class3)starclusters.Inaddition,wehavemadeuseoftheequationsin Tuckeretal. ( 2006 )totransformourphotometryintoSDSSugrizstandardlters.Figure 3-4 showsthecolor-magnitudediagrams(CMDs)andcolordistributionsofoursample(class1and2)ascomparedwiththeconrmedstarclustersfromtheSMcatalog(class3).ThemagnitudedistributionofoursamplecontainsmorefaintstarclustersthanSM.The 53

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Galletietal. 2004 )andanaveragereddeningcorrectionofE(V-I)=0.06( Sarajedinietal. 2000 ).Thecolorrangeofoursampleissignicantlywiderthanthecolorrangeoftheconrmedclusters:.4<(gr)<1.5and.0<(ri)<1.0.Thelowerpanelsshowaunimodaldistributionwithastrongpeakat(gr)0.1and(ri)0.2havingextendedtailsredwardin(gr)colorandbluewardin(ri). 3-5 showscolor-colordiagramsofthecandidatestarclusters.Tocomparewithsimplestellarpopulations(SSP),twodifferentsetsofmodelshavebeenused: Bruzual&Charlot ( 2003 ,BC03)and Kotullaetal. ( 2009 ,Galev).BC03modelscorrespondtoanevolutionarytrackforaninstantaneousburstandaSalpeterIMFwhileGalevmodelscorrespondtoacustomizedsetprovidedtousbyRalfKotullaandtheGalevteam.TheGalevSSPmodelswererunassumingGenevaevolutionarytrackswithaminimumageandtimeresolutionof0.1Myrsuntil100Myrs,andatime-stepof1Myrsforolderages.ThemodelswererunwithaSalpeterIMF(1-120M)fordifferentmetallicities.ItisimportanttonotethatGalevmodelsincludecontributionsfromnebularemission,consideringthecontinuumnebularandalsoemissionlines.Alloftheclustershavebeenshiftedbyaline-of-sightreddeningvalueofE(V-I)=0.06( Sarajedinietal. 2000 )andadoptinganextinctionrelationfrom Cardellietal. ( 1989 ).Comparisonsbetweentheintegratedclustercolorsandthepredictionsofstellarpopulationmodelscanprovideageestimatesthatarepotentiallyusefulforstudiesofgalaxyevolution.However,uncertaintiesinagesderivedfrommulti-colorphotometrycomenotonlyfromthephotometricerrors,butalsofromreddeningcorrectionsanduncertaintiesinthemetalabundanceofeachcluster.Furthermore,theface-onviewofthegalaxyandthenumerousspiralarmsproduceabroadrangeofreddeninginM33thatcanscattertheintegratedcolorsofindividualclusters.Anothereffectthatisimportantinthisregardisthedispersionintheintegratedcolorsduetostochasticeffects 54

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Color-colordiagramofthecandidatestarclustersfromthepresentstudy(blackcircles)ascomparedwiththeconrmedclustersfromSM(greencircles).ThesolidlinescorrespondwiththeSSPmodelsof( Bruzual&Charlot 2003 ,BC03)and( Kotullaetal. 2009 ,Galev)forz=0.019andz=0.0004.Alltheclustershavebeenshiftedbyaline-of-sightreddeningvalueofE(VI)=0.06( Sarajedinietal. 2000 ).TheredcrosscorrespondswiththeintegratedcolorsofthenucleusofM33andthearrowsinthetopleftcornersrepresentthedirectionofthereddeningvector. 55

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Girardietal. 1995 ).TheadoptedIMFintheSSPalsocontributestouncertaintiesinthemodels.Giventhesepoints,wehavenotattemptedtoestimateagesbasedontheintegratedphotometryoftheclusters.Inanycase,thecolor-colordiagramsrevealanumberofinterestingfeatures.Asignicantfractionof`bluish'clustersthatoccupyauniquelocationinthediagramappearinbothpanelsofFigure 3-5 atcolors(ri)<.2and(ui)<0.8.Theseclustersrepresentanger-likefeaturethatdeviatesfromtheexpecteddirectionofevolution.AtleastveconrmedclustersfromSMareassociatedwiththefeature,supportingtheclusternatureoftheseobjects.Theageestimatesforthreeofthemshowsages107yrs.BasedonthelowerpanelinFigure 3-5 ,the'nger'featurecouldbeassociatedwiththepresenceofasignicantpopulationofveryyoungclusters(<107yrs)exhibitingnebularemission.Thepositionofmanyofthembelowthetheoreticallineisconsistentwithinternalreddeningshiftingtheircolorstoreddervaluesconsistentwiththedustycloudsinwhichtheyareborn.Figure 3-6 showsthespatialdistributionoftheseveryyoungclustersonaGalexFUVimage.Acloseinspectionofthisimagesuggeststhatalltheclustersareassociatedwithregionsofstarformationactivity.Therecentworkof Grossietal. ( 2010 )analyzesmulti-wavelengthobservationsof32youngstarclustersandassociationsinM33.ThesamplewasselectedfromcatalogsofemissionlineobjectsbasedontheirroundshapeandtheirpositioninregionsofthegalaxythatarenottoocrowdedintheHmap.Alloftheobjectshaveoxygenabundancesof8<12+log(O/H)<8.7andhave24mcounterpartsintheSpitzer/MIPSmap.Comparisonofthe Grossietal. ( 2010 )catalogandoursreveals10commonobjects,allofthemassociatedwiththepreviouslymentioned'nger'feature.Table 3-1 providesacross-identicationofthecommonobjectsandincludestheages,extinctionsandreddeningsobtainedfromtheirspectralenergydistribution(SED)ttingtechnique.Thisresultconrmstheyoungageoftheseclusters,youngerthan12Myr, 56

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GalexFUVimageofM33.Theimagetracesthestarformationregionsofthegalaxythroughitsyoungstars.Theblacktrianglescorrespondtothe56starclustercandidatesassociatedwiththenger-likefeature. 57

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Grossietal. ( 2010 ) Id(Us)Id(Grossi)logAgeaAvaE(B-V)aClassicationb Grossietal. ( 2010 )bProposedclassicationasinTable C-1 3-5 revealsawideragerangeof1Myrs10Gyrswithatleast50%ofobjectscorrespondingtoyoungclusters(<100Myrs)and10%ofthetotalcorrespondingtoveryyoungclusterswithnebularemission(nger-likefeature).Inspiteoftheredwardtailat(gr)>0.7thatisprobablycausedbyreddening,thediagramsuggeststhepresenceofanoldpopulationatleastasoldas10Gyr.Furthermore,theintegratedcolorsofthenucleusofM33(RA=01:33:51.02;DEC=30:39:36.68)havebeenplottedinthecolor-colordiagramsofFigure 3-5 andFigure 3-6 .Afterexaminingthecurveofgrowthfordifferentaperturediameters,wehaveadoptedanapertureradiusof4.4forthemagnitudemeasurementsandabackgroundskyof7.5and9.Theintegratedlightshowsabluenucleuswithu=14.9,(ui)=0.92,(ug)=0.63and(ri)=0.33. 58

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Bicaetal. ( 1991 )amongLMCstarclustersinthe(UB)vs.(BV)diagram.TheLMCgapwasnoticedat(UB)'0.19and(BV)'0.47withanapproximatewidthof0.1maginbothcolors.TheupperpanelinFigure 3-7 showsasmallregionoftheLMCandM33color-colordiagramsforbettervisualizationofthegaps.TheLMCdataarefrom Bicaetal. ( 1996 )andhavebeenconvertedtotheSDSSugrizsystemusingrelationspublishedby Jesteretal. ( 2005 ).ConstantreddeningvaluesofE(VI)=0.06( Sarajedinietal. 2000 )andE(BV)=0.1( Alvesetal. 2002 )havebeenadoptedforM33andLMC,respectively.AlthoughtheM33gapappearsbluerinthediagram,bothgapscorrespondtoasimilarrangeinage.ThelowerpanelinFigure 3-7 showsthecolordistributionoftheM33andLMCclusters.Toavoidcontaminationbyclustersinthenger-likefeature,whichcorrespondstoadifferentagerange,onlyclusterswith(ug)>0.4havebeenconsideredintheconstructionofthecolordistribution.ThegapinM33lookssmallerandslightlyredderthanthegapintheLMC.Theoffsetcouldbeaconsequenceofthereddeningcorrectionwehaveappliedwhichdoesnotaccountfordustinternaltoeachgalaxy.Severalauthors( Renzini&Buzzoni 1986 ; Sweigartetal. 1990 )haveinterpretedtheLMCgapasbeingproducedbytheredgiantbranchphasetransition.Thistransitionwouldbeproducedbystarsattheheliumashstageandwouldttheoreticalpredictions. Girardietal. ( 1995 )disagreeswiththisinterpretationandarguesthatthelackofclustersinthisregionisdeterminedbythenaturaldispersionofthecolors.Thestochasticeffectsonthemassdistributionofstarscouldproducethedispersioninthecolorssonoadditionalpeculiaritieswouldbeneededinthestellarmodelsinordertoreproducethisfeatureofthediagram.However,thediscoveryofthegapamongM33 59

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Bicaetal. 1996 )intherelevantcolorrangesforabettervisualizationofthegaps.Toavoidcontaminationofclustersthatexhibitnebularemission,onlyclusterswith(ug)>0.4(dashedline)havebeenconsideredinthecolordistribution.Lowerpanel:Colordistributionofoursample(unlledhistogram)andLMC(lledhistogram).M33gapcanbedetectedat(gr)'0.3and(ug)'0.8.,andtheLMCgapat(gr)'0.3and(ug)'1.3. clusterssupportsthepresenceofanevolutionaryeffectatthatparticularageastheoriginofbothgaps. 3-8 presentsthecolor-magnitudediagramsoftheclustersystemofoursample,theMilkyWay(MW),M31andtheLargeMagellanicCloud(LMC).TheMWdatabelongto Lataetal. ( 2002 )(openclusters)and Harris ( 1996 )(globularclusters).TheM31datacorrespondtothecandidateandconrmedclustersin Peacocketal. ( 2009 ).DatafortheLMCclustersystemfrom Bicaetal. ( 1996 )havealsobeenplotted.Inordertocomparethedifferentclustersystems,wehaveplottedabsolutemagnitudesandreddeningcorrectedcolors.TheMWabsolutemagnitudesaretakendirectlyfrom 60

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Color-magnitudediagramsofstarclustersindifferentgalaxiesoftheLocalGroup:a)TheMilkyWay:openclusters(opencircles)( Lataetal. 2002 )andglobularclusters(lledcircles)( Harris 1996 );b)M31( Peacocketal. 2009 )c)LMC( Bicaetal. 1996 )andc)M33conrmedandcandidatestarclustersfromthisstudy.ThedashedlinesrepresentthedivisionofGalacticglobularclustersat(BV)0=0.5. theabove-mentionedcatalogsassumingaspecicdistancemodulusandreddeningforeachcluster.WehaveadoptedaLMCdistancemodulusof18.50( Freedmanetal. 2001 )and24.36forM31( Vilardelletal. 2010 ).ConstantreddeningvaluesofE(VI)=0.06( Sarajedinietal. 2000 ),E(VI)=0.1( Durrelletal. 2001 )andE(BV)=0.1( Alvesetal. 2002 )havebeenadoptedforM33,M31andtheLMC,respectively.Ifneeded,wehaveusedthe Jesteretal. ( 2005 )transformationstoconvertabsolutemagnitudesintotheg-band.ThedashedlinesrepresentthedivisionofGalacticglobularclustersat(BV)0=0.5.NodistinctclustersubpopulationscanbeidentiedwithintheM33clustersystemlikeintheLMCorMW.However,theintegratedcolorsoftheveryyoungclustersare 61

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3-7 ),thecolor-magnitudediagramshowsapossiblebimodality.TheM33andLMCsystemsaredominatedbyblueclusters,(BV)0<0.5,incontrastwiththeredderM31system.However,whiletheredclustersubpopulationofLMCoccupiesaverynarrow(gr)0region,M33redclusterspopulateasignicantlywidercolorrangemoresimilartoM31redclusters.Whencomparingtheabsolutemagnitudesoftheclustersystems,weseethatthebrightestclustersintheMWandLMCreachluminositiesofMg.5;however,thebrightestclustersinM33correspondtoMg,morethanonemagnitudefainter.Thiseffectcouldbeexplainedbytherelationbetweenthestarformationrate(SFR)ofagalaxyandthemaximummass/luminosityofitsstarclusters( Larsen 2002 ).TheempiricalrelationsuggeststhatgalaxieswithhighSFRsformproportionallymoreclusters,andasaconsequence,theclustermassfunctionreacheshighermasses.AssumingaSFRof0.45Myrs1,theclustersystemofM33wouldtontothisrelationreasonablywell(seeFigure1 Bastian ( 2008 )).WiththeslightlyhigherSFRfortheMW,LMCandM31(eg. Kangetal. ( 2009 ), Robitaille&Whitney ( 2010 ))thesesystemswillproducebrighterclusters.Inaddition,environmentalvariations,suchasthemass/luminosityofthegalaxy,canplayaroleinthecolor-magnitudediagramofaclustersystem( Mieskeetal. 2010 ).Figure 3-9 presentsthecolor-colordiagramsoftheM33clustersystemusingoursample,M31andLMC.Thesourcesofthedataarethesameasthosegivenabove.Asareference,SSPmodelsfromtheGalevteam( Kotullaetal. 2009 )withametallicityofz=0.0004havebeenoverplotted.Toidentifydifferenttimeperiods,thestarsymbols 62

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Color-colordiagramsofthecandidatestarclustersfromthepresentstudy(blackcircles)ascomparedwiththecandidateandconrmedclustersinM31(greencircles)( Peacocketal. 2009 )andconrmedclustersintheLMC(bluecircles)( Bicaetal. 1996 ).ThesolidlinecorrespondstotheSSPmodelsof Kotullaetal. ( 2009 )withametallicityofz=0.0004.Thestarsymbolscorrespondtoagesof106,107,108,109and1010yrsandtheredcrosscorrespondswiththeintegratedcolorsofthenucleusofM33. 63

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Barmbyetal. 2006 ; Chandaretal. 2004 ).AlthoughNGC300isnearlyatwingalaxyofM33intermsofHubbletypeandmass,thereareseveraldifferencesbetweenthem( Gogartenetal. 2010 ).NGC300appearstohaveglobularclusterssimilartothoseoftheMilkyWay( Nantaisetal. 2010 )andametallicitygradientconsistentwithstarsformedpriorto6Gyrsago( Gogartenetal. 2010 ).EnvironmentalfactorsmayplayakeyroleinthestarformationhistoryofM33,asNGC300isisolatedfromothergalaxieswhileM33appearstobeinteractingwithM31( McConnachieetal. 2009 ; Putmanetal. 2009 ). McConnachieetal. ( 2009 )proposeaplausibleM31-M33interactionmodelthatreproduceswithgoodagreementtheobserveddistances,angularpositionsandradialvelocitiesofthesegalaxiesaswellasthewell-knownHIwarpinM33.Inthissimulation,M33startsitsorbitaroundM31about3.4Gyrsagoreachingpericenter(r56kpc)around2.6Gyrsago.Afteritpassesapocenter(r264kpc)about900Myrsago,M33wouldbeapproachingM31.Thiscloseencountercouldhavetriggeredanepochof 64

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Whitmore&Schweizer ( 1995 ); Gallagheretal. ( 2001 )),especiallyveryyoungclusters.Wewouldexpecttoseeveryyoungclustersstillembeddedintheirdustcocoonsinthesedisturbedsystems.Yet,theircolor-colordiagramsdonotexhibitasprominentanger-likefeatureduetonebularemissionaroundveryyoungclustersascomparedwithM33(seeAntenna( Whitmore&Schweizer 1995 );Stephan'squintet( Gallagheretal. 2001 )).IntheunusualenvironmentofHicksoncompactgroup31(HGC31), Gallagheretal. ( 2010 )foundalargepopulationof<10Myrstarclusterswithstrongnebularemission,similartotheonefoundinthepresentstudy.ThemaingalaxiesthatmakeupHGC31aredisruptedunderthepresenceofstronggravitationalinteractionsandshowtidalstructures.ThestarclustercandidateswithnebularemissionappearthroughoutHCG31,specicallyconcentratedintheinteractionregions.TheexistenceoftheseveryyoungstarclustersseemstobetheconsequenceofactiverecentandongoingstarformationinHGC31.ThesimilaritiesbetweentheM33clustersystemandthatofHGC31,whichisastronglyinteractingenvironment,supporttwoimportantassertions.First,thenger-likefeatureisagenuinecharacteristicandnotanarticialeffectduetothecontaminationofourclustersample.Second,thepastinteractionsbetweenM33andM31havelikelyhadsignicantimpactonthepropertiesoftheM33clustersystem,especiallytheyoungestclusters. 65

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Cumulativeradialdistributionforthestarclusters(thisstudy)andeldstars( Hartmanetal. 2006 )inM33. remainingclusterswecategorizeasblueoryoungobjects.Thispartitionminimizesthecontaminationoftheold(red)clustersbytheyoungclustersinthenger-likefeaturewhichexhibitintegratedcolorsthatareredderthattheexpected.Inordertoplacetheclusterdensitydistributioninthecontextoftheeldstars,wehavemadeuseofthe Hartmanetal. ( 2006 )starcatalogconstructedoverthesameMegaCam/CFHTimagesusedinthepresentstudy.Figure 3-10 showsthecumulativeradialdistributionsoftheyoungandoldclusterspopulationsascomparedwiththeblue(young)andred(old)eldstarpopulations.Blueclustersfollowaspatialdistributionsimilartotheblueeldstars.Thedistributionalsosuggeststhatyounger(bluer)clustersaremorecentrallyconcentratedascomparedwitholder(redder)clusters.Theredclustersaremoredispersedinawiderregionthanthebluerones,indicatingthatthemajorityofthered(old)clusterslikelybelongtothe 66

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Radialdensitydistributionofourclustersample(lledcircles)ascomparedwiththeeldstars(smalldots)from Hartmanetal. ( 2006 )versusdeprojectedradius.Thesolidlinerepresentsthebestpolynomialtoftheeldstarradialdensity.Asacomparisonwithpreviouscatalogs,opencirclescorrespondtotheconrmedclustersinSM. halowhilethebluer(younger)clustersgenerallybelongtothediskofM33.AnalysisofthesedistributionsusingaKolmogorov-Smirnov(KS)testshowsthatthereisagreaterthan99.9%chancethattheoldclusterpopulationissignicantlydifferentthantheyoungclusterpopulation.Figure 3-11 showstheradialdensitydistributionofourentireclustersample.Thelledcirclesshowtheclusterdensityproleversusdeprojectedradius,assumingouradopteddistancemodulusof(mM)0=24.69,whiletheopencirclesshowtheconrmedclustersfromSMforcomparison.Thesmalldotscorrespondwiththeradialdensitydistributionoftheeldstarswherethesolidlinerepresentsthebestpolynomialt.Thestardensitydistributionhasbeenscaledtomatchtheclusterdensityintheregion 67

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Forbesetal. 1996 ).Ourradialproles,showninFigure 3-11 ,havereducedthediscrepancybetweentheclustersandeldstarsbuttheformerarestillmorecentrallyconcentratedthanthelatterasshownbythecumulativedistributionsinFigure 3-10 .Thepronounceddecreaseat15kpcintheclusterandeld-stardensitydistributionssuggestthatthisdistancemayrepresenttheouteredgeofbothdistributions.Foragivenradialbinintheouterregionofthegalaxy,thedensityofclustersissignicantlylowerthanthedensityofstars.Wenotethepossibilitythattheclusterandstellarsamplesmayhavedifferentcompletenessproperties.Inordertominimizethepotentialimpactofincompleteness,werestrictthecomparisonofthesesamplestotheregionoutside0.8kpcfromthecenterofthegalaxy.Iftheincompletenessofoursampleisthereasonforthedifferencesbetweentheclusterandeldstarradialproles,thenwewouldexpectarandombiasorperhapsalargerincompletenesstowardthecenterofthegalaxy.However,theanalysisshowsasignicantlylowerdensityofclustersbetweenR=39kpcthanintheinnerregionbetweenR=0.83kpc.Theratioofstarstoclustersisdeterminednotonlybytheformationprocessesbutalsobythedestructionprocesses.Ifweassumethattheformationofstarclustersandtheformationofstarsinagalaxyarecorrelated,thenFigure 3-11 suggeststhattheclustersysteminM33hassufferedfromdestructionordepletionofclustersatspecicradii.Tidalinteractionswhenpassingthroughthediskornearmassiveobjects 68

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Gielesetal. ( 2006 ); Lamersetal. ( 2005 )).Analysisofthedynamicalevolutionoftheseclustersisneededtorevealthelevelofinuenceoftheseinteractionsinthedisruptionprocess.OtherenvironmenteffectssuchasinteractionsbetweenM33andM31canalsoplayaroleinthedepletionordisruptionofclustersatpreferredgalactocentricdistances. Huxoretal. ( 2009 )discoveredthepresenceoffournewoutlyingstarclustersinM33whichhavelargeprojectedradiiof38113arcmin(9.628.5kpc).Basedontheasymmetryinthedistributionoftheseouterclusters,theysuggestthepossibilitythatinteractionswithM31mayhavedramaticallyaffectedthepopulationofM33starclusters.Regardlessofthesourceofthisanomaly,wewouldneedanadditional350clustersbetweenR=39kpcinordertomatchthestellardensityinthesameregionofthegalaxy.Ifwerescalethedensityofstarstomatchtheclusterdensityintheouterregion,anotableexcessofclustersoccursatR<4kpc.Thisscenarioishighlyunlikelysincedynamicaldestructionprocessesaremoreeffectivenearthecentralregionofagalaxy.Theshortlifetimeofsuchayoungsampleofclustersalsomakestheclustermigrationscenarioimplausible.Nocasehasbeenfoundinwhichtheclusterdensityexceedsthestardensityintheinnerregionofagalaxy.Futurefollow-upsofthissamplewilltestthevalidityofthedepletionphenomenonthatcouldhavewidespreadrepercussionsforourunderstandingofM33'sformationandevolution. 69

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King 1962 1966 ).MoreextensiveKing-basedmodelsexistthattakeintoconsiderationnon-isotropicsystems,rotatingsystemsorevenmulti-massmodels(e.g. Michie 1963 ; Wilson 1975 ; DaCosta&Freeman 1976 ).Thesecondfamilyofmodels,knownasEFF(forElson,Freeman,andFall)models,wereempiricallyderivedtoreproducethesurfacebrightnessprolesofyoungclustersintheMagellanicClouds( Elsonetal. 1987 ; Elson 1991 ).Theseprolesaredescribedaspower-lawsthatdonotincludethepronouncedtidaltruncationoftheKingmodels.ItiswellknownthatKingmodelsprovideanexcellentdescriptionoftheluminosityprolesandinternalkinematicsofmostMWglobularclusters(e.g. Djorgovski 1995 ; Trageretal. 1995 ; McLaughlin 2000 ).Highspatialresolutiondataarerequiredtostudystructuresinextragalacticclusters.HubbleSpaceTelescope(HST)imaginghasbeensuccessfullyusedtotavarietyofmodelstothesurfacebrightnessprolesofclustersinM31( Barmbyetal. 2002 2007 2009 ),theMagellanicClouds(MC),andtheFornaxdwarfspheroidalgalaxy( Mackey&Gilmore 2003a b c ; McLaughlin&vanderMarel 2005 ).Thesestudiessuggestthatglobularclusters(GCs)describeafundamentalplaneanalogoustothefundamentalplaneofellipticalgalaxies.Morphologicalstudiesofyoungerclusterspresentmoredifcultiesbasedontheir,generally,lowerconcentrationandmass;itisnotwellestablishedifopenclusters(OCs)intheMWalsolieonthesamefundamentalplane( Bonatto&Bica 2005 ; Barmbyetal. 2009 ).Therefore,itis 71

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2 ; 3 ; Cockcroftetal. 2011 ).However,structuralstudiesofthissystemareverylimited. Larsenetal. ( 2002 )presentstructuralparametersderivedfromKingmodeltsforfourGCsinM33.Dynamicallyandstructurally,theyappearvirtuallyidenticaltotheMWandM31GCs,andtverywellintothefundamentalplane. Chandaretal. ( 1999b )presentcoreradiiof60starclustersusinglinearcorrelationswiththemeasuredfullwidthathalfmaximum(FWHM)ofeachcluster.TomitigatethecurrentlimitedknowledgeonthemorphologyofM33starclusters,wehaveundertakenacomprehensivestructuralstudyofthelargestsampleofM33starclusterstodate.ThisChapterpresentstheresultsofthisstudyandisorganizedasfollows.Section 4.1 describestheobservationsanddatareduction.Section 4.2 presentstheanalysisofellipticitiesandpositionangleswhileSection 4.3 discussesthesurfacebrightnessprolesandtheprolettings.TheanalysisofthestructuralparametersandcomparisonwithothergalaxiesareshowninSection 4.4 .Finally,Section 4.5 presentsasummaryofthestudy. 2 ( SanRomanetal. 2009 ),andforadetaileddescriptionwereferthereadertothatChapter.Forconvenience,weprovideanabbreviatedsummarybelow.TheobservationswereobtainedwiththeAdvancedCameraforSurveysWideFieldChannel(ACS/WFC)onboardtheHST.TwelveHST/ACSeldsfromtheGO-10190program(P.I.:D.Garnett)havebeenanalyzed.Threelterswereusedfortheprimaryobservations(F475W,F606W,F814W)andtwofortheparallelimages(F606W,F814W).Figure 2-1 inChapter 2 showsthelocationsoftheseeldswhileTable 2-1 presentsasummaryoftheobservations. 72

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Sarajedinietal. ( 2006 ).ThisPSFwasusedtoconvolvethestructuralmodelsbeforethettingprocess.Thepipeline-processeddrizzled(DRZ)imageswereusedtoconstructthesurfacebrightnessphotometry.WederivedpositionaloffsetsbetweentheseframesusingtheimshiftandimcombinetasksinIRAFtoallowustoproduceonemasterimageperlterpereld.Tomakethecalculationofthephotometricerrorsmorestraightforward,eachDRZimagewasmultipliedbytheexposuretimebeforeperformingthephotometry,andthenthebackgroundskyvaluewasaddedbacktoeachimage. Larsenetal. 2002 ; Barmbyetal. 2002 ; McLaughlinetal. 2008 ). 73

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4-1 showstheellipticityandPAprolesasafunctionofsemi-majoraxisforarepresentativesampleofclusters.ThearbitraryuctuationsintheellipticitiesandPAatsmallradii(<0.5)arelikelytobeproducedbyinternalerrorsintheELLIPSEalgorithm.Inthefarouterpartsoftheclusters,theellipticityandPAarepoorlyconstrainedduetothelowsignal-to-noiseratio.Giventhesefacts,thenalellipticityandPAforeachclusterwerecalculatedastheaverageofthevaluesbetween0.5and1.5wherethequantitiesaremorestable.Inmostofthecases,theellipticityiswelltracedinthedifferentlters.In12cases,thefaintnessoftheobjectsprohibitedusfromanaccuratedeterminationoftheellipticityinboththeF606WandF814Wlters.Forsmallellipticities,thePAisnotwelldeterminedandvariessignicantlybetweenlters.Wemadeanerrorcutinthevaluesandwedonotincludethesepoorlycontrainedvaluesinthenalcatalog.Table D-1 inAppendix D showstheellipticitiesandPAsforthestarclustersampleidentiedinChapter 2 intheF606WandF814Wlters.Errorscorrespondwiththestandarddeviationofthemean.Somestudieshavesuggestedthatclusteratteningisgenerallyattributabletoclusterrotationeffectsratherthangalactictides( White&Shawl 1987 ; Davoust& 74

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Ellipticitiesandpositionanglesasafunctionofsemi-majoraxesforarepresentativesubsampleofthetotalclustersample.SolidlinescorrespondtovaluesfromF606WimageswhiledottedlinescorrespondtoF814Wimages.Positionanglesarecountednorththrougheast.TheidenticationnameofeachclustercorrespondwiththenotationinChapter 2 75

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, 1990 ).Duringthedynamicalevolutionoftheseobjects,theylosemassandangularmomentum.Asaconsequence,clustersrotateslowerandbecomerounderastheyevolve.ToinvestigatetheelongationoriginofM33SCs,Figure 4-2 showsdifferentclusterpropertiesasafunctionofellipticity.TheclusterpropertiesweredeterminedandanalyzedinChapter 2 .EllipticitiesinM33clustersdonotseemtobedrivenbyanyoftheclusterpropertiesplottedinFigure 4-2 .Thedistributionsofclusteratteninginnearbygalaxiesareknowntobeverydifferent(e.g. vandenBergh 2008 ).EllipticitiesinGalacticGCshavebeenfoundtocorrelateinverselywithage,suggestingstructuralchangesovertimeorchangesintheinitialconditions( Frenk&Fall 1982 ).ThecorrelationoftheellipticitywiththeageandmassinLMCandSMCclustersarefoundtobeweak( Goodwin 1997 ; Hill&Zaritsky 2006 ).OurM33sampledoesnotshowanyclearcorrelationwithageormass.Aluminosityellipticityrelationhasalsobeensuggestedinsomenearbygalaxies( vandenBergh 2008 ).Whilethefaintestclustersassociatedwithmassivegalaxies(MW,M31andNGC5128)areatterthanthemostluminousstarclusters,noevidenceforaluminosityellipticitycorrelationexistsintheLMCorSMC.Nocorrelationbetweenmagnitudeandellipticityisfoundinoursampleeither. Elson ( 1991 )suggestthatthehighellipticityobservedinmanyoftheyoungLMCclusterscouldbeduetothepresenceofsubclumps.However,suchsubstructureswouldbeerasedasclustersevolve.ThemeanellipticityofstarclustersintheMWandM31issmallerthanthatoftheLMC,whichisinturnsmallerthanthemeanellipticityofstarclustersintheSMC.Ithasbeensuggestedthatthisiscorrelatedwiththemassesofthesegalaxies( Geisler&Hodge 1980 ; Stanevaetal. 1996 ). Goodwin ( 1997 )suggeststhetidaleldstrengthoftheparentgalaxyasthedominantfactordrivingthedifferencesbetweentheLMCandtheMWstarclusters.Tidalforceswoulddestroytheinitialanisotropicvelocitydispersionsofacluster,modifyingitsinitialshape.Thiseffectwouldbemuchless 76

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Clusterellipticitiesversusmass(M),age,galactocentricdistance(Rgc),VmagnitudeandV-Icolor.TheclusterpropertieswereadoptedfromChapter 2 77

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Meanellipticityofstarclustersasafunctionoftheirhostgalaxyluminosity. signicantinthelessmassivegalaxiessothetidaleldintheLMCwouldnotbeabletomodifysignicantlytheshapesofitsclustersmaintainingtheirinitialtriaxiality.ThisscenariowouldalsoexplaintheevenhigherellipticitiesobservedintheSMC.Figure 4-3 showsthemeanellipticityofdifferentstarclustersystemsasafunctionoftheluminosityoftheirhostgalaxy.Themeanellipticitieswereobtainedfrom Harris ( 1996 )fortheMW, Barmbyetal. ( 2002 2007 )forM31, vandenBergh ( 2008 )fortheLMCand Hill&Zaritsky ( 2006 )fortheSMC.ThemeanellipticityforclustersinM33correspondstothemeanvaluefromTable D-1 .Theerrorofthedatacorrespondswiththestandarddeviation.Theluminositiesforeachgalaxyareadoptedfrom vandenBergh ( 1999 ).Withameanellipticityofe=0.2,M33clustersare,onaverage,moreattenedthanthoseoftheMWorM31andmoresimilartoclustersintheMCinagreementwiththisscenario. 78

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ClusterelongationsandorientationsrepresentedintheRA-Deccoordinateplane.Northisupandeastistotheleft.Thevectorsizesarecorrelatedwiththeellipticityobtainedinthisstudy.ThecrosscorrespondswiththecenterofM33,withthearrowmarkingthepositionangle(23o)ofthegalaxy( Regan&Vogel 1994 ). Ontheotherhand,tidaleldsarealsoabletostretchclustersandmakethemmoreelongated.IftidalforceshaveadominanteffectontheelongationofM33clusters,onewouldexpectapreferredorientationoftheSCpositionanglestowardsthelocationoftheforce.Figure 4-4 summarizestheelongationandorientationoftheclusterswithrespecttothegalaxy.Thereisnocleartrendintheorientationvectorstowardthegalacticcenter,howevertheorientationoftheclusterstendstohaveapreferreddirection.Inparticular,thepositionangledistributioninFigure 4-5 showsabimodalitywithastrongpeakat55o.ThisnorthwestdirectionpointstowardM31,whichislocatedatapositionangleofabout40owithrespecttothecenterofM33.RecentevidencesuggeststhatacloseencounterbetweenM33andM31couldhaveaffected 79

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Distributionofthepositionangles(PA)ofoursample. thepropertiesoftheM33disk.Duetothesmallgalactocentricdistanceoftheseclusters(Rgc<7Kpc),theideaofM31asthesourceoftheelongationseemsunlikely.AnalysisofthePAsshownocorrelationwithage,mass,distanceormagnitudeoftheclusters.Nocorrelationhasbeenfoundwiththespiralarmpatternorwithcircularorbitsaroundthegalaxy.Theelongationoftheclustersarenotalignedwiththex-ypixelcoordinatesystemofeachsetofimages,rulingoutapossibleartifactrelatedtoclusterorientation.ThesignicanceofthepreferredorientationoftheM33clustersremainsopenandfurtherinvestigationofthisphenomenonwillrequireprecisePAsofabiggersampleofclustersatdifferentlocationsinthegalaxy. 80

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Barmbyetal. ( 2007 )totransformtherawoutputvaluesfromELLIPSEtocalibratedsurfacebrightnessesontheVegamagsystem.Wehaverstconvertedimagecounts(countspixel1)intoluminositydensityinLpc2.Wehaveworkedintermsoflinearintensityandnallytransformtheresultstosurfacebrightnessmagnitudeunits(/magarcsec2).TheprolesextendedouttoR=14(63pc)inbothlters.Figure 4-6 showsexamplesofclustersurfacebrightnessproleswheretheerrorbarsareestimationsobtainedbyELLIPSEfromtheisophotalintensities.Appendix D includesthesurfacebrightnessprolesforalltheclustersinoursample. 4-6 showsexamplesofmoretraditionalprolesversusFigure 4-7 thatshowsexamplesofclusterproleswithdifferentirregularities.Foradetailedinspection,wehaveoverplotted3concentricapertures,0.1,0.5and1.0,ontheF606Wimages.Morethanhalfofoursampleexhibitssomelevelofanomaly.Someofthesefeaturescouldbetheresultofstatisticaluctuationsorduetoafewluminousstars.However,sub-clumpsoradecitofstarsarealsoprominentinasignicantnumberofclusters(e.g.clusters12,24,71),andappeartoreectrealstructureswithintheclusters.Objectswithirregularitiesareobservedalongtheentirerangeofageswithnopreferenceatanyparticularstageofevolution. Hill&Zaritsky ( 2006 )identifysimilaranomaliesamongSMCstarclusterproles.Theydetect,inseveralsurfacebrightnessproles,systematicdeviationsfromtheanalyticalmodelsthattheyattributetoalackofcentralconcentration.Theyrefertotheseclustersasringclustersandsuggestthattheseanomaliescouldbetheresultofdynamicalevolution.Someoftheclusterscouldbeintheprocessofdissolution 81

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Surfacebrightnessprolesandmodeltstoarepresentativesampleofclusters.LeftpanelscorrespondwithF606WprolesandrightpanelswithF814W.Thesolidlineineachpanelrepresentsthebest-tKingmodelwhilethedottedlinerepresentsthebest-tEFFmodel. 82

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SameasFigure5butforagroupofclustersshowingirregularitiesintheirproles.EachrowcorrespondswithadifferentclusterwithleftpanelshowingtheF606WproleandrightpaneltheF814Wprole.Thebottomrowshowsa5x5F606Wimageofthe3clusters.Forvisualguiding,the3concentricaperturescorrespondwithradiiof0.1,0.5and1.0. 83

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Elson ( 1991 )reportsbumps,sharpshoulders,andcentraldipsintheprolesofLMCclusterswithanagerangesimilarthanoursample.Theyinterprettheseanomaliesasconsequencesoftheinitialconditionsorsignaturesofmergingsub-condensations.Oursampledonotshowanycorrelationbetweenthepresenceoftheseirregularitiesandanyotherparameter.SimilarirregularitieshavealsobeendetectedamongLMCclustersatalowerdegreeby Mackey&Gilmore ( 2003b ). King 1962 )ofsingle-mass,isotropicandisothermalspheres: [1+(R=Rc)2]1 21 [1+(Rt=Rc)2]1 2)2(4)where0isthecentralsurfacenumberdensityofthecluster,Rcisthecoreradius,andRtisthetidalradius.Itisusefultodenetheconcentrationparameterasc=log(Rt/Rc).However,youngLMCclustersdonotappeartobetidallytruncated,andseemtobemoresuitablyttedbypower-lawproles. Elsonetal. ( 1987 )argueinfavorofanunboundhalocausedbytheclusterexpansionduetomasslossorviolentrelaxation,andproposedanempiricaldescriptionknownastheEFFmodel: 84

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(1 SanRomanetal. 2009 ,fordetails)beforetheminimizationprocess.Fromthetotalsampleof161clustersinChapter 2 ,33objectswererejectedduetolowsignal-to-noiseratios.Figure 4-6 showstheclustersurfacebrightnessproleswiththebest-ttingmodelswheretheerrorbarsareestimationsobtainedbyELLIPSEfromtheisophotalintensities.Theparametersfromthebest-tKingmodelaregiveninTable D-2 inAppendix D ,withTable D-3 presentingtheparametersfromthebest-tEFFmodel.Clusterswithatypicalproles,Figure 4-7 ,deviatefromtheanalyticalmodelsinspecicregions,nevertheless,eveninthosecasesourmeasurementsreectthesizesoftheclustersandtheircores.Thelistederrorsinthetables,aregivenbythe2minimizationttingprocess.Alternatively,thedifferencebetweentheF606WandF814Wtscanbeusedasamorerealisticuncertainty.WenotethatadistancetoM33of870kpc(distancemodulus=24.69; Galletietal. 2004 )hasbeenadoptedduringthettingprocess.Nineclusters,withavailablestructuralparameters,arecommonto Chandaretal. ( 1999b ).Directcomparisonbetweencoreradiigivesusoffsetsof:Rc(CBFUs)=0.810.3pc.Theprolesofthoseobjects,exceptintwocases,haveprominentirregularitiesintheirproles. Chandaretal. ( 1999b )calculatecoreradiiusingalinearcorrelationwithFWHMratherthandirectmodelts.Thediscrepancybetweenthetwo 85

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QualityofthetofEFFmodelrelativetoKingmodelversusageandhalf-lighradiusforthetwodifferentlters. studiescanbecausedbythedifferentadoptedmethodsinadditiontothepeculiarproles.Following McLaughlin&vanderMarel ( 2005 ),wedeneastatisticalparameterthatcomparesthe2ofthebesttofbothmodelsforanyobject: 4-8 showsthisparameterasafunctionofageandhalf-light 86

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SanRomanetal. ( 2009 ),wheretheywereobtainedviacolor-magnitudediagram(CMD)tting.Youngclusters(Logage<8)arenotablybettertbymodelswithnoradialtruncation.Inolderclusters,smallvaluesofthestatisticparameter,.20.2,shownosignicantdifferencesbetweenthequalityofthettings.EFFmodelsarealsofavoredforsmallersizesasshowninthebottompanelofFigure 4-8 WorkingwithF606WandF814Wprovidesuswithtwoindependentsetsofmeasurementsforeachcluster.Systematicerrorsandcolordependenciesinthetscanbeevaluatedthroughdirectcomparisonofbothmeasurements.Figure 4-9 comparestheparametersderivedfrommodeltsinF606WandF814W.Theresultsshowgoodagreementbetweenbands.WeonlyconsidertheF606Wmodeltsfromnowonbecausethislterismoresensitivetotheunderlyingstellarpopulation,andlesssensitivetoforegroundcontaminatingstars.Inaddition,tstoclustersinothergalaxiesaretypicallyperformedintheV-bandallowingusdirectcomparisonwithoutbeingconcernedaboutpossiblecolorgradients.SinceKingmodelsareprimarilyusedtodescribeclustersinothergalaxies,weadoptthederivedKingstructuralparametersasthebasisforthesubsequentanalysis. 4.4.1ComparisonwithOtherGalaxiesThedynamicalevolutionofstarclustersdirectlyaffectstheirstructuralproperties.Therefore,comparingstructuralparametersindifferentgalaxiesisofspecialimportancetounderstandstarclusterevolutioninavarietyofenvironments.WehavecomparedthenewlyderivedM33structuralparameterswiththoseforclustersinM31( Barmbyetal. 2007 ),theLMCandSMC( McLaughlin&vanderMarel 2005 )inVmagnitude.Thesesampleshavebeenanalyzedinanearlyhomogeneousway.Figure 4-10 showscorrelationsamongdifferentstructuralparameters.Wehaveincludedthefourold,haloM33GCsanalyzedin Larsenetal. ( 2002 ).Theyappear 87

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Comparisonofhalf-lightradiusobservedinbothF606WandF814Wltersforthedifferentttedmodels. tohavesimilarstructuralpropertiesthanoursampleexceptforthehigherbrightness.Allofthegalaxiespresentsimilartrendsalthoughseveraldifferencesstandout.M33seemstopossessclusterswithsmallsizes,notshowingobjectswithradiibetweenRc=310pcobservedinothergalaxies.Withanaverageofc=1.12,theconcentrationinM33clustersissmallerthanthemeanconcentrationsofclustersintheMW(c=1.41),M31(c=1.46)andLMC(c=1.46).Thetop-rightpanelinFigure 4-10 showsthatthecentralsurfacebrightnessofM33starclustersarefainterthantheoneinM31andLMCstarclusters,coveringasmallerrangeandpresentingaslightlyoffsetpositioninthediagram.Ingeneralmoremassive/luminousclusterstendtohavebrighter0.ThebrightestclustersinM33aremorethan1magfainterthanthebrightestclustersintheMW,M31andLMC( SanRomanetal. 2010 )soonewouldexpectM33starclusterstohavefaintercentralsurfacebrightness. 88

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StructuralparametersofthepresentstudyascomparedwithstarclustersinM31( Barmbyetal. 2007 ),LMCandSMC( McLaughlin&vanderMarel 2005 ).RcandRhareplottedinlogarithmicscaleforbettercomparison. StructuralpropertiesfortheM33sampleareshownasafunctionofestimatedageinFigure 4-11 .Whenpossible,wehavecomparedoursamplewiththeabovestudies.AgesforM31clustersareadoptedfrom Caldwelletal. ( 2009 )forthecommonobjects,whileagesforLMCandSMCareprovidedintheirpreviouslymentionedstudies.Comparisonbetweenthesegalaxiessuggestssimilartrends.Theage-radiusrelationamongM33clustershasbeenpreviouslysuggested( Chandaretal. 1999b )andalsoobservedindifferentgalaxies(e.g. Mackey&Gilmore 2003a b ; Glattetal. 2009 ). Elsonetal. ( 1989 )identied,amongLMCclusters,acleartrendthatthespreadincoreradiusisanincreasingfunctionofclusterage.Thistrendwasconrmedlaterby 89

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StructuralparametersofthepresentstudyversusageascomparedwithM31( Barmbyetal. 2007 ),LMCandSMC( McLaughlin&vanderMarel 2005 ) Mackey&Gilmore ( 2003a )usingHSTimages. Elsonetal. ( 1989 )suggestmasslossfromstellarevolutionasthecauseofclusterexpansion.Allclusterswouldhaveformedwithsmallcoreradiiandasthemostmassivestarsevolvetheywouldexpand.Thetrendofolderclustershavingalargerrangeincoreradiithantheyoungerpopulationisclearlyvisibleinthetop-rightpanelofFigure 4-11 .Atintermediateages,theRcspreadinM33clustersislargerthanamongtheLMCclusterssotheseclusterswillsuffersignicantandrapidmasslossfromstellarevolution.Theinitialmassfunction(IMF)governstherateofexpansionsovariationsintheIMFslopecouldberesponsible. Wilkinsonetal. 90

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2003 )investigatethedynamicaloriginofthecoreradiusevolutioninLMCstarclustersusingN-bodysimulations.Theyconsideratime-varyingtidaleldandvariationsinprimordialbinaryfractionsaspossibleexplanations.TheyconcludethatthetidaleldoftheLMCdoesnotinuencetheevolutionoftheclusterssignicantly.Thepresenceoflargenumbersofprimordialbinariesinaclusterleadstocoreradiusexpansion;howeverthemagnitudeoftheeffectisinsufcenttoexplaintheobservationsinLMCclusters.Eventually,thistendencywouldbereversedatolderagesproducingcore-collapseclusters.Weobservethiseffectamongoldclusters(LogAge>9.5)intheSMCandthefouroldM33globularclustersfrom Larsenetal. ( 2002 ). vandenBergh 1991 ; Djorgovski&Meylan 1994 ).Similarresultshavebeenfoundinnearbygalaxies( Barmbyetal. 2002 ).Thesestudiesshowthatstarclustersatlargegalactocentricdistances,onaverage,havelargerdiametersthanthoseclosertothegalacticcenter.Whilelargeclusterswithsmallgalactocentricdistancescouldhavebeendisrupted,thereisnosatisfactoryexplanationforthedeciencyofsmallclustersatlargerdistances.Forthisreason,thiscorrelationhasbeensuggestedtobeaninitialphysicalconditionofclusterformationandageneralpropertyofstarclustersystems( vandenBergh 1991 ).Onlyprojecteddistancesareavailableforoursample.Nocorrelationhasbeenfoundbetweenconcentrationandgalactocentricdistance,Rgc.CentralsurfacebrightnessdoesnotcorrelateeitherwithRgc.ToexploretheRhRgcrelation,we 91

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Barmbyetal. ( 2007 ),andusetherenormalizedgalactocentricdistanceasabetterindicatorofgalacticpotentialthangalactocentricdistanceitself: Corbelli&Salucci 2000 ),230forM31( Carignanetal. 2006 ),65fortheLMC( vanderMareletal. 2002 )and60fortheSMC( Stanimirovicetal. 2004 ).Figure 4-12 showsRhasafunctionofrenormalizedgalactocentricdistance,Rgc,forthedifferentgalaxies.ThelledcirclesinthetopleftpanelrepresentoursampleofM33clusters,andthestarsymbolscorrespondwiththefourglobularclustersin Larsenetal. ( 2002 ).Thesolidlinecorrespondswiththeleast-squarestofthecombinedsample.ThesolidlinesfortherestofthegalaxieshavebeentakenfromTable10( Barmbyetal. 2007 )asthesuggestedSCfundamentalplanets.NoclearcorrelationhasbeenfoundintheM33sample.Only5conrmedclustershavebeendetectedintheoutskirtsofM33(Rgc>10kpc)( Stonkuteetal. 2008 ; Huxoretal. 2009 ; Cockcroftetal. 2011 ).Whenthese5clustersareincludedintheanalysis,thedatashowasimilartrendthaninothergalaxies(TopleftpanelofFigure 4-12 ).Theveouterclustersarerepresentedasopensymbols,andthenewleast-squarestcorrespondswiththedashedline.Whilethetrendinothergalaxiesisclearlydrivenbysmallinnerclustersandalsolargeclustersatlargerradii,thecorrelationinM33isjustforcedbyverylargeclustersintheouterpartofthegalaxy.Thiscouldbeaselectioneffectsinceatlargedistances,smallclusterswillbedifculttodetectinground-basedimages.High-resolutionimaginghasshownthattheoverallpropertiesofGCsindifferentgalaxiesareremarkablysimilar.Infact,severalstudiessuggestthatGCstructuralanddynamicalpropertiescanbesummarizedasdescribingafundamentalplaneanalogoustotheoneforellipticalgalaxies( Djorgovski 1995 ; Dubath&Grillmair 1997 ; 92

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Half-lighradiusasafunctionofrenormalizedgalactocentricdistanceforclustersinoursample,M31,MWandMC.Solidlinesrepresenttheleast-squarests.Inthetopleftpanelsolidlinerepresenttheleast-squarestincludingoursample(lledcircles)andthefourGCsin Larsenetal. ( 2002 ).OpencirclesinthesamepanelcorrespondwithoutskirtclustersinM33( Cockcroftetal. 2011 ).Thedashedlinecorrespondstotheleast-squarestincludingoursampe, Larsenetal. ( 2002 )and( Cockcroftetal. 2011 ). McLaughlin 2000 ).Dynamicallyandstructurally,thefourM33clustersstudiedin Larsenetal. ( 2002 ),appearvirtuallyidenticaltoMWandM31globularclusters.TheanalysisofoursamplesuggestsseveraldifferencesbetweenstructuralpropertiesofM33clustersandclustersinnearbygalaxies.Thesedifferencescouldbeexplainedbythedisparehostenvironments.MeasurementsofvelocitydispersionsforalargesampleofM33clusterswouldpermitpreciseM/LratiostodeterminewithcondenceifM33clustersfallinthesuggestedfundamentalplaneforMWandM31clusters. 93

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4 ,M33possessarichclustersystemthatpopulatesalmostallevolutionaryphases,includingagesandmetallicitiesnotobservedintheMWorM31.Inadditiontoaprominentyoung-intermediatepopulation,M33starclustercolor-colordiagramsrevealasignicantpopulationofred,presumablyoldclusters.Therefore,M33providesanidealopportunitytostudyclusterkinematicsasafunctionofage.Largemoderntelescopesprovideadequatesignal-to-noisetoconstraintheearlyformationhistoryofM33throughkinematicanalysisofthesered/oldclusters.SpectroscopicstudiesofM33clustersareverylimitedandcanbesummarizedintwocontributions.Intherstcontribution, Schommeretal. ( 1991 )presentvelocitiesfor45starclusterscoveringarangeofagesbetween0.110Gyr.Thestudysuggeststheexistenceofakinematichaloofoldclusters,withavelocitydispersionof70 95

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Chandaretal. ( 2002 )presentvelocitymeasurementsfor107starclustersfromahomogeneousdatasetthatspantheentirerangeofclusterages.Inagreementwithformerresults,theyndthattheclustervelocitydispersion,withrespecttothelocaldiskmotion,increasesdramaticallywithage.Thisanalysissuggeststwocleardistinctsubpopulations,ahaloandadiskcomponent.Inadditiontothediskandhalocomponents, McConnachieetal. ( 2006 )identifyamongeldstarsathirdkinematiccomponentwhichtheysuggestcouldbeatidalstreaminM33.DetailedstudiesoftherotationcurveandinternalmotionsofHIgasandHIIregionsyieldmoreinformationaboutM33kinematics.High-resolutionobservationsofneutralhydrogenprovidemassdistributionandrotationalvelocitiesofthecoldgasinthegalaxy. Warneretal. ( 1973 )obtainasystemicvelocityofkm/s1km/s,aninclinationangleof543,andapositionangleof222. Zaritskyetal. ( 1989 )measurevelocitiesfor55HIIregionsandndvaluesingoodagreementwiththeparametersderivedfromHIgasmeasurements.ThecurrentunderstandingofM33kinematicpropertiesisstillinarudimentarystage.InthischapterweperformakinematicstudyofstarclustersintheaforementionedM33catalog.Therecentknowledgeacquiredandpresentedinpreviouschaptersiscompletedherewithspectroscopicstudyofoursample.Inparticular,weareinterestedinusingspectroscopicdatatoidentifykinematiccomponentsinM33suchasdisk,halo,andpotentialstellarstreams. 96

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SanRomanetal. ( 2010 ).TheM33nucleuswasalsoobservedtomeasurethesystemicvelocity.Inaddition,somestandardstarswereobserved. 97

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5-1 .Startingwiththetoppanelandmovingdown,thesespectraillustratetypicallinestrengthsfoundineachagedivision.ThestrengthofmetallinesincreaseswithclusteragewhilenarrowerBalmerlinesarepresentinyoungerclusters.Formostoftheclustersinoursample,ageswereestimatedfromintegratedphotometry,exceptforobjectsfrom SanRomanetal. ( 2009 ),whereageswereobtainedbyisochronetting.Twotechniqueshavebeenusedtomeasuretheline-of-sightclustervelocities.ThersttechniquewasperformedusingtheRVIDLINES/IRAFtaskthatmeasurestheradialvelocitiesbydeterminingthewavelengthshiftinspectrallinesrelativetospeciedrestwavelengths.Thecentersoftheabsorptionlinesaretted,andthewavelengthshiftsmeasured.Thenalobservedvelocitieswereconvertedtoheliocentricvelocities.Between6and10lineswereusedtoobtainedthenalradialvelocityfortheGTCspectraandbetween4and7fortheWHTspectra.ThebroadBalmerlineandtheweakmetalliticyfeaturesofveryyoungclusterslimitthevelocitymeasurements,makingaccuratevelocityinyoungclustersdifculttoobtain.ThesecondtechniquewasperformedusingtheFXCOR/IRAFtaskthatusesaone-dimensionalFouriercross-correlationbasedonthestandard Tonry&Davis ( 1979 )algorithm.Thistechniquecorrelatesanobjectspectrumwithatemplatetocalculatethe 99

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GTC/OSIRISspectraforseveralclustersinoursample.Theidenticationnumberofeachclustercorrespondswith SanRomanetal. ( 2010 ).Theageofeachclusterwasobtainedfrom Sarajedini&Mancone ( 2007 ). relativeshiftbetweenthetwo.Duringthecorrelation,stronglinesareweightedmorethanweakones.Inaddition,thistechniquehastheadvantageofusingalltheavailableinformationpresentinthespectrumratherthanonlyafewlines.Previously,thespectrawererebinnedtothesmallestdispersionbetweentheobjectandtemplatespectra.Thecontinuumfrombothspectrawasalsosubtractedinordertoreducepotentialsecondarypeaksproducebynoise.Furthermore,aramplterwasappliedtothespectrato 100

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Warneretal. 1973 ),andwiththevalueof6km/sobtainedby Chandaretal. ( 2002 ).Weobtainedvelocitiesof9km/sand8km/sforR12=SR1765,usingtherstandsecondtechniquerespectively.Bothvelocitiesareinperfectagreementwithvaluesfrompreviousstudies,10km/s( Chandaretal. 2002 ).Table 5-1 providesthederivedclustervelocitiesfromtheGTCobservationsusingbothtechniques.Clusterobservationsthatgavepoorcorrelation(lessthan0.4)donothavelistedFXCORvelocities.ForobservationsperformedwithWHT,onlyRVIDLINESvelocitiesareprovidedinTable 5-2 .VelocitiesofobjectsobservedwithWHTandobtainedusingtheFXCORtechniquewillberenedandimprovedwiththeadditionalobservationsfromtheabovementionedWHTserviceprogramme. IdaLogageVcluster(RVIDLINES)Vcluster(FXCOR)VdiskAlterId.b(yrs)(km/s)(km/s)(km/s) 14589.62061781203...137952075...147402176510.09...31612558.3c136117

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IdaLogageVcluster(RVIDLINES)Vcluster(FXCOR)VdiskAlterId.b(yrs)(km/s)(km/s)(km/s) 12589.2212812111339.125376615968.1c...2022010668.3c10285315258.1c221619116218.1c81323110318.8c10144914468.1c203317612398.4c131211012497.8c32...11413898.1c214416213198.2c202214113617.2c91415414378.2c172517412327.7c153553113887.8c172554818497.8c82859615528.1c171820115108.0c13957316317.8c2245582 2 ( SanRomanetal. 2010 )bIdenticationnumberin Sarajedini&Mancone ( 2007 )cAgesderivedfromisochronetting( SanRomanetal. 2009 ). Table5-2.KinematicPropertiesofM33StarClusters(WHTObservations) IdaLogageVcluster(RVIDLINES)VdiskAlterId.b(yrs)(km/s)(km/s) 1303...2013812339.0221031330...35147893...45...73210.31110204...29...578...22...11648.517802140...20...

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IdaLogageVcluster(RVIDLINES)VdiskAlterId.b(yrs)(km/s)(km/s) 19577.81137120438.9939217109.11627519018.51935513447.7c19545...6.616...238...6.98...420...7.5c45...565 2 ( SanRomanetal. 2010 ).bIdenticationnumberin Sarajedini&Mancone ( 2007 ).cAgesderivedfromisochronetting( SanRomanetal. 2009 ). 5.3.1ComparisonwithPreviousStudiesVelocitiesfromourrsttechniquegivemeasurementsinreasonableagreementwiththosefromFouriercross-correlation.AmeandifferenceofV(RVIDLINESFXCOR)=6.94.3km/sisobtainedbetweenbothtechniques,wheretheerrorcorrespondswiththestandarddeviationofthemean.DuetothelimitedamountofvaluesobtainedfromFouriercross-correlation,onlyvelocitiesdeterminedwiththersttechniquearegoingtobeconsideredforthefollowinganalysis.Fifteenoftheobjectsinthisstudyoverlapwith Chandaretal. ( 2002 ).Figure 5-2 showsthevelocitycomparisonofthecommonobjects.Allofthem,exceptforone,haveconsistentvelocitymeasurementswithintheuncertainties.Velocityvaluesfrom Chandaretal. ( 2002 )wereobtainedusingFouriercross-correlation.Excludingtheclusterwithaclearindividualdiscrepancy,thesampleshowsanoffsetofV(UsChandar)=.45.2km/sbetweenthetwostudies.Azeropointinthetemplateusedineachstudycouldaffecttheresultsproducingasystematicoffset.Possiblesourcesofindividualdiscrepanciescouldbeproducedbythesignal-to-noiseoftheobjects.Overallresultsshowthatweobtainvelocitiesingoodagreementwiththosefrompreviousstudies. 103

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Comparisonoftheradialvelocitiesfromthepresentstudywiththoseof Chandaretal. ( 2002 ).Thedashedlinecorrespondswiththeonetoonecorrelation. Schommeretal. 1991 ; Chandaretal. 2002 ),wecomparethevelocityoftheclusterswiththemotionoftheM33diskatthatspecicposition.Analysisofthevelocitydispersionswithrespecttothediskmotioncandetermineiftheclustersaremovingwiththediskorbelongtoadifferentkinematiccomponent.Youngobjectsborninthediskhavenothadtimetointeractwithmassiveobjectslikemolecularcloudsthatpotentiallycouldchangetheirvelocity.Incontrast,olderobjectscouldhaveamoredisorderedmotion.TheradialvelocityeldofM33hasbeenwellstudiedthroughtherotationcurve,andinternalmotionsofHIgasand 104

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Warneretal. ( 1973 )presenttheradialvelocityoftheM33diskouttoagalactocentricdistanceof6kpcusingHImeasurements.Followingtheirprescription,theobserveddiskvelocitycanbedeterminedby: Warneretal. 1973 ).ForV(R),weinterpolatetherotationalcurvepresentinTable1of Warneretal. ( 1973 ),andobtainthespecicvaluesfortheclusterpositionsinoursample.Thederiveddiskvelocity,Vdisk,arepresentedinTable 5-1 andTable 5-2 .Figure 5-3 showsthevelocitydispersionwithrespecttotheM33diskmotionasafunctionofage.Wehavealsooverplottedresultsfrom Chandaretal. ( 2002 ).Thegureshowsasignicantlyincreaseinvelocitydispersionwithrespecttothediskmotionwithage.Thesmallnumberofold(>109yrs)starclustersinoursampledoesnotallowus,atthemoment,forfurtheranalysisofthatagedivision.However,oursampleincreasesnotablythenumberofintermediateageclusters(108109yrs),anagerangenotwellpopulatedin Chandaretal. ( 2002 ).Theseintermediateageclustersshowasimilarbehaviorthanclustersin Chandaretal. ( 2002 )butwithalargerdispersionvelocity.Themeandispersionvelocityforclustersinthatagerangeinoursampleis=20.6km/s,absolutevaluesignicantlylargerthanthe=6km/s 105

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ClustervelocitydispersionrespecttheM33diskmotionasafunctionofage. forthesameagerangemeasuredby Chandaretal. ( 2002 ).Typicaluncertaintiesforclustervelocitiesinthisplotare15-25km/s.Aspreviouslymentioned,integratedcolorsaretheprimarysourceforagedeterminationsinM33,producingsignicantuncertaintiesinthemeasurements.Inaddition,nometallicityvaluesareavailabletobreaktheage-metallicitydegeneracy.ChemicalcompositionandagefromspectroscopicstudiesarerequiredforabetterinterpretationofFigure 5-3 .Analysisofthevelocitiesalongthemajoraxiscanshowwhetherasystemisrotatingornot.Figure 5-4 showstheradialvelocitiesoftheclustersasafunctionofgalactocentricdistanceprojectedalongthemajoraxis(distanceoftheclustersfromtheminoraxis).Specialconsiderationisgiventointermediateageclusters(lledcircles)forwhichthebestlineartisplottedasasolidline.Forcomparisonaformallinearrotation(solid-bodyrotation)ofthedisk,asobtainedfrom Warneretal. ( 1973 )rotation 106

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Radialvelocityoftheclustersasafunctionofdistancefromtheminoraxis.Filledsymbolscorrespondwithclusterswithagesbetween108109yrswhereopensymbolscorrespondwiththerestofthesample.Thebestlineartfortheintermediateageclustersisoverplotted(solidline).ForcomparisonthedashedlinecorrespondswiththediskrotationofM33. curve,isoverplotted(dashedline).Consideringtheradialcoverageofoursample,asolid-bodyrotationisanadequateapproximation.Thelineartsgiveusaslopeof.2kms1kpc1forthenetrotationofthediskandaslopeof.9kms1kpc1fortheintermediateageclusters.Theintermediateageclustersrotatewithlargerdispersionthanthediskwithnosignicantnetrotation.Aclusterwitharadialvelocity
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Sarajedini&Mancone 2007 ),previouscatalogsofM33starclusterssufferedfromsevereincompleteness,especiallyintheoutskirtsofthegalaxy.Tomitigatethisincompleteness,amajoreffortofthisstudyhasbeenfocusedinhavingastatisticallymeaningfulensembleofobjects.Ingeneral,ground-basedimagingcannotclearlydistinguishstarclustersfromothertypesofextendedsourcesbutHSTprovidesthespatialresolutionnecessaryforanunequivocaldetermination.WhileHSTanditsseveralinstrumentshavebeensuccessfullyusedinthesearchforstarclusters,thesmalleldofviewpermitssurveysonlyoveralimitedregionofthegalaxy.Forthesereasons,wehaveundertakenground-basedandspace-basedsurveysthatcomplementeachother.Inourspace-basedsurvey,Chapter 2 ( SanRomanetal. 2009 ),wehaveanalyzed12ACS/HSTelds.FourprimaryeldswereobtainedalongthemajoraxisofM33.Eightcoordinatedparalleleldswerealsosecuredalongbothsidesoftheprimary-eld 109

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3 ; SanRomanetal. 2010 ).TheobservationsforthisstudywereobtainedonlinethroughtheCanadianAstronomyDataCentre(CADC)archive.TheimagesweretakenusingMegaCamwide-eldmosaicthatoffersnearlyafull1x1eldofviewwithahighangularresolutionof0.817pix1.Inordertofacilitatethesearchforclustercandidates,onlythebestavailableimageswereanalyzedin5lterswithmedianseeingvaluesoflessthan0.7.OurdetectionmethodisbasedonthefactthatatthedistanceofM33,non-stellarobjectsareexpectedtobemoreextendedthanthePSF.AftersubtractingthestellarPSFfromallofthesourcesinourframes,extendedobjectsleaveadoughnut-shapedappearance,astheyareunder-subtractedinthewingsandover-subtractedinthecenter.Whilemostbackgroundgalaxiesshoweitheraspiralarmstructureoranelongatedpattern,thecandidatestellarclustersshowsomelevelofassembly.After 110

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6-1 showsanillustrationofourground-basedandspaced-basedsurveys.InChapter 4 ,wediscussthemorphologicalpropertiesofthe161starclustersanalyzedin SanRomanetal. ( 2009 ).Wepresent,forthersttime,ellipticities,positionangles,andsurfacebrightnessprolesforasignicantnumberofclusters.Ellipticitiesofthesampleshowthat,onaverage,M33clustersaremoreattenedthanthoseof 111

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A1x1centeredonM33.Northisupandeastistotheleft.Theredcirclesshowtheconrmedclustersin Sarajedini&Mancone ( 2007 ),including SanRomanetal. ( 2009 ),wherethebluecirclescorrespondwiththecandidateclustersin SanRomanetal. ( 2010 ).TheeldofviewrepresentstheareaobservedwiththeMegaCamcamera(36CCDs,greenrectangles)andascomparisontheblacksquaresrepresentthe4HST/ACSprimaryeldsfromourspace-basedsurvey. 112

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5 ,wepresentvelocitymeasurementsof45starclustersinM33fromintegratedspectroscopy.TheobservationsforthisstudywereobtainedthroughGTC/OSIRISlong-slitspectrographandWHT/WYFFOSmulti-berspectrograph.Ourpreviouscatalogprovideduswiththetargetsamplewherealltheobjectshavebeenpreviouslyconrmed,andagesandphotometryareavailable.Oursampleshowsthatthevelocitydispersionwithrespecttothelocaldiskmotionincreaseswithageforyoungandintermediateclusters,withameanvaluesignicantlylargerthaninpreviousstudies.Analysisoftheintermediateageclustersshowsthattheyrotatewithalargerdispersionthanthediskwithnosignicantnetrotation.FurtheranalysisofalargersamplecoulddetermineunambiguouslyiftheintermediateageclustersinM33belongtoahalokinematiccomponent. 113

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Corbelli&Walterbos 2007 )andahalowithluminositylessthanafewpercentofthediskluminosity( Fergusonetal. 2007 ),M33wasalwaysbeenthoughttobetheperfectexampleofapurediskgalaxy.Inaddition,exceptfortheouterHIdisk,therewerenosignsofinteractionsorrecentmassivesatelliteaccretion,supportingtheideaofagalaxyinisolation.ThePan-AndromedaArchaeologicalSurvey(PAndAS)isaprogrammedesignedtoexplore,indetail,thestructureandcontentofM31andM33.RecentresultsfromthissurveyndnewsignaturesintheoutskirtofM33,favoringapreviouscloseencounterbetweenM31andM33,andsuggestingamorechallengingevolutionofM33.AspartofthePAndASproject, McConnachieetal. ( 2009 )ndapreviouslyunknownprominentstellarstructuresurroundingM33.Thisfeaturehasanextensionstretching2(30kpcprojected;threetimesfartheroutthantheclassicaldiskofM33)tothenorthwest,towardsM31,withasecondextensionvisibleinthesouth. Grossietal. ( 2011 )alsosuggestthatthestellardistributionatlargeradiiisdisturbedwithevidenceoftidalinteractionoraccretionevents. McConnachieetal. ( 2009 )proposeaplausibleM31-M33interactionmodelthatreproduceswithgoodagreementtheobserveddistances,angularpositions,andradialvelocitiesofthesegalaxiesaswellasthewell-knownHIwarpinM33.Inthissimulation,M33startsitsorbitaroundM31about3.4Gyragoreachingpericenter(r56kpc)around2.6Gyrago.Afteritpassesapocenter(r264kpc)about900Myrago,M33wouldbeapproachingM31.Inour 114

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3 ,wehavealsofoundadecitofclustersatlargegalactocentricdistancesandwesuggestinteractionswithM31asapossiblesourceofdisruptionordepletion. Huxoretal. ( 2009 )discoverthepresenceoffournewoutlyingSCsinM33whichhavelargeprojectedradiiof38'113'(9.628.5kpc).Basedontheasymmetryinthedistributionoftheseouterclusters,theysuggestthepossibilitythatinteractionswithM31mayhavedramaticallyaffectedthepopulationofM33SCs.Recently, Cockcroftetal. ( 2011 ),aspartofthePAndASsurvey,haveextendedthesearchofhalostarclustersoutsideourground-basedsurvey( SanRomanetal. 2010 ),coveringover40deg2andusingdeeperCFHT/MegaCamimages.Theyndonlyonenewunambiguousstarclustersinadditiontothevepreviouslyknown( Huxoretal. 2009 ; Stonkuteetal. 2008 ).InaggreementwithourresultsfromChapter 3 ,theysuggestalackofouterhaloclusterswhencomparedwiththeM31halo.TheyattributethisdecittoeithertidalstrippingofM33'souterhaloclustersbyM31,oraverydifferent,muchcalmeraccretionhistoryofM33.Theultimategoalofthisdissertationistoincreaseourunderstandingofthegalaxyformationprocess.However,theresultsfromtheseresearchprojectswillbeofessentialrelevanceformanyotherareasintheeldstarclusters.Forexample,themechanismsofclusterdestructionarestillnotclear.Thereisnoconsensusregardingtheamountofdisruptionobservedortheroleofclustermassandenvironmentintheprocess.Oneofthemainproblemsliesinthedifcultyofproducingcompleteclustersamplesindifferentenvironments.Sincethestar-formationrateinM33isknowntohavebeenconstantforthelast1Gyr,theM33starclustersystemisidealforconstrainingthedisruptionmechanismsofclusters,orforstudyingtheinitialmassfunction(IMF)ofthe 115

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3 ,containsthedeepestandwidest-eldground-basedM33starclustercatalogto-dateandwillhelptoresolvethosequestions.Intheshortterm,weareinterestedindoingfurtherspectroscopicworkinoursampleofstarclusters.WewillbeabletodetermineagesandmetallicitiesbymakinguseofLick/IDSindicesandcomparingtheresultswithupdatedmodels.Wewilldeterminemeanchemicalabundanceswithaprecisionof0.2dexforstarclustersinadiversityofregionsofM33.WewillsearchforsubstructuresinthevicinityofM33aswellascharacterizethestructureofitsdiskandhalo.Wewillapplyforadditionaltimeinsubsequentsemesterstoincreasethenumberofobjectsandtomakeuseofthehigherspectralresolutionandthemulti-slitmodethatwillbeavailableonGTC/OSIRISinthenearfuture.M33isjustonecaseofasubstantialpopulationofnearbydwarfspirals.Asanexample,NGC300isgalaxynearlyidenticaltoM33intermsofHubbletypeandmass.However,NGC300appearstohaveglobularclusterssimilartothoseoftheMilkyWay(MW).EnvironmentalfactorsmayplayakeyroleinthestarformationhistoryofM33.WhileNGC300isisolatedfromothergalaxies,M33appearstobeinteractingwithM31.ThroughthisdissertationwehavelaidthefoundationforsubsequentstudiesofotherdwarfspiralgalaxiesintheLocalVolume.Thisstudywillprovidekeyinsightsintothestarformationhistory,compositionandkinematicsoflow-massgalaxies,aswellasplacedwarfspiralgalaxieswithinthecontextofthegalaxyformationprocess. 116

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IDRA(J2000)Dec(J2000)V(V-I)(B-V)E(V-I)LogAgeaMassbNotesAlt.Idc

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IDRA(J2000)Dec(J2000)V(V-I)(B-V)E(V-I)LogAgeaMassbNotesAlt.Idc Note.UnitsofRAarehours,minutes,andseconds,andunitsofDecaredegrees,arcminutes,andarcseconds.aUnitsofageareinyears.bUnitsofmassare103McAlternativeIdenticationnumberin Sarajedini&Mancone ( 2007 )dErrorinLogAgeof0.1.

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IdR.A.Decl.g(u-g)(g-r)(g-i)(g-z)EllipticityFWHM()StellarityAlt.IdaClassif.b

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IdR.A.Decl.g(u-g)(g-r)(g-i)(g-z)EllipticityFWHM()StellarityAlt.IdaClassif.b

PAGE 248

IdR.A.Decl.g(u-g)(g-r)(g-i)(g-z)EllipticityFWHM()StellarityAlt.IdaClassif.b Note.ThecompletetablealsoincludestheoriginalCFHTlters(ug'r'i'z')magnitudesanderrorsforthecandidatesSCs.UnitsofR.A.(J2000.0)arehours,minutes,andseconds,andunitsofDecl.(J2000.0)aredegrees,arcminutes,andarcseconds.aAlternativeidenticationnumberin Sarajedini&Mancone ( 2007 )bProposedclassiciation:-1:galaxy,0:unknownextendedobject,1:candidateSC,2:highlyprobableSC,and3:conrmedSC(basedonSMcatalog).Thistableisavailableinitsentiretyinamachine-readbleformin SanRomanetal. ( 2010 ).

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IdaEllipticityEllipticityPAPA(F606W)(F814W)(F606W)(F814W) 10.230.010.290.0263.42.664.22.220.250.04.........3............40.140.030.180.04......5............60.170.020.170.03......70.230.020.250.0164.52.062.71.580.050.010.140.02......9............100.170.03.........110.140.020.200.02......120.300.040.330.03......130.160.03.........140.220.030.220.0263.14.162.45.4150.430.030.380.02-40.94.3-52.75.7160.210.020.220.03......170.150.020.180.03......180.290.04.........190.130.020.100.01-46.33.9-45.63.8200.190.040.170.03......210.360.02.........220.060.010.090.02......230.280.03.........240.240.020.150.02......250.190.020.250.0341.74.237.85.6260.260.030.290.02-62.04.3-58.24.4270.120.030.130.02......280.140.00...-70.00.0...290.250.050.330.04......300.230.010.230.01-69.43.2-66.43.6310.240.030.260.02......320.240.020.260.02......330.090.01...-30.05.1...34............350.270.030.370.02......

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IdaEllipticityEllipticityPAPA(F606W)(F814W)(F606W)(F814W) 360.140.000.220.00-70.00.0-75.10.0370.230.020.180.0367.51.2-28.025.2380.120.000.170.03-58.30.0-23.617.4390.450.020.400.0138.63.230.90.4400.210.020.190.03......410.190.010.120.00......420.340.020.350.00......430.200.030.230.02......440.400.04.........450.120.020.130.02......460.240.040.120.02-42.17.4-30.920.5470.280.010.260.0155.42.855.92.1480.330.010.420.01-80.81.9-33.822.2490.160.030.170.03......500.280.010.270.02......510.240.010.260.01-51.52.5-43.41.9520.310.01...11.30.1...530.230.030.360.02......540.180.040.240.04......550.180.020.170.0320.92.224.26.6560.230.030.330.01......570.110.010.110.02......580.120.020.140.04......590.160.02...-64.910.1...600.440.000.360.0528.90.014.36.161............620.130.010.100.00......630.170.020.190.02-53.95.5-59.44.2640.230.030.130.03-55.35.6-35.45.4650.130.020.240.01......660.300.030.240.02......670.160.020.190.04......680.440.000.480.01-53.30.9-51.50.8690.180.030.130.03-22.13.5-24.57.1700.260.030.370.05......710.140.020.170.04-37.78.2-56.24.4720.120.020.140.03......

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IdaEllipticityEllipticityPAPA(F606W)(F814W)(F606W)(F814W) 730.280.010.260.01......74............750.370.030.310.02-56.22.1-54.31.3760.180.040.190.04-60.67.9-67.07.8770.330.010.280.02-12.20.9-2.33.9780.180.020.170.03-58.19.325.817.8790.270.020.270.02-48.40.1-56.81.2800.210.020.260.0251.21.064.51.3810.120.010.100.02-54.36.8-50.114.2820.070.010.090.01......830.190.010.160.0138.86.641.06.0840.240.03.........850.290.010.320.0214.41.914.51.2860.310.010.300.02-14.81.8-11.82.1870.240.020.270.03......88............890.220.03.........90............91...0.390.01......920.270.01.........930.230.020.420.0386.21.753.018.3940.310.030.220.03-61.93.1-62.74.7950.200.030.200.03......960.100.020.250.03......970.120.010.170.02......980.210.030.180.03......990.320.000.340.01-38.72.3-37.42.5100...0.490.01......1010.250.010.230.02-34.87.2-27.78.01020.220.020.220.02......103............1040.160.030.190.02-35.97.2-25.416.71050.090.000.130.02......1060.190.020.170.03-21.64.6-29.35.61070.250.030.280.0338.87.356.76.91080.080.010.250.02......1090.300.020.250.03-24.81.3-17.12.5

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IdaEllipticityEllipticityPAPA(F606W)(F814W)(F606W)(F814W) 1100.190.020.280.03......1110.220.050.210.05......112............1130.150.05.........1140.250.010.240.0280.02.320.624.91150.250.010.340.03......1160.440.000.430.0076.30.069.70.01170.260.050.200.00......118............1190.180.010.140.0170.25.019.423.51200.250.040.380.05-50.96.0-48.74.21210.220.020.290.03......1220.160.010.200.01-49.24.9-45.05.11230.130.020.160.03......1240.240.010.290.03-8.01.7-11.22.41250.190.030.260.03-59.51.7-52.51.21260.110.020.140.03......1270.200.03...-51.63.9...128............1290.120.030.170.0331.16.432.25.11300.210.020.200.01......1310.120.030.120.02......1320.210.030.190.0345.14.549.33.41330.170.020.180.02......1340.130.010.190.02......1350.340.040.380.0443.55.851.55.81360.100.010.260.02......1370.170.030.160.01......1380.330.02...-41.90.4...1390.110.020.110.02......1400.160.020.160.02......1410.190.000.370.02......1420.110.010.200.04......1430.290.020.220.0068.914.7-86.30.01440.310.040.350.01......1450.270.00...-65.46.3...1460.180.020.240.05-45.07.5-74.03.6

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IdaEllipticityEllipticityPAPA(F606W)(F814W)(F606W)(F814W) 1470.310.000.370.00-32.70.0-25.50.01480.240.040.230.04......1490.180.010.200.02......1500.180.030.240.03......1510.200.000.250.0361.90.0-9.512.21520.250.040.330.03-64.53.8-46.417.81530.280.040.260.0330.12.233.71.81540.260.02...-72.01.3...1550.340.010.290.01......1560.250.020.330.0379.21.177.11.61570.340.010.240.02-22.51.5-19.95.11580.160.020.110.02......1590.140.020.190.02......1600.210.030.240.03-60.05.8-66.04.71610.200.03...-33.07.0... 2

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) 1F606W19.380.020.220.000.920.022.470.0910.430.361.060.020.390.011.630.0334.960.25F814W18.690.020.210.000.900.022.410.0810.160.331.050.020.380.011.600.0339.820.282F606W19.180.020.100.000.410.01...............37.470.28F814W19.030.010.140.000.570.01...............42.160.263F606W21.400.060.790.043.350.163.840.1916.190.790.680.030.930.033.940.1336.900.32F814W20.920.100.320.021.340.08...............42.500.384F606W18.210.020.090.000.390.012.830.2211.920.921.480.040.270.011.130.0436.710.20F814W18.240.010.100.000.440.013.000.3712.651.551.460.050.290.021.230.0743.170.265F606W20.640.030.190.000.790.02...............42.600.36F814W20.570.080.220.010.940.054.001.6516.866.951.250.180.500.102.090.4250.110.396F606W19.420.020.220.000.940.024.600.6719.412.841.320.060.530.042.230.1640.150.29F814W18.970.030.220.010.910.037.372.6431.0911.141.530.160.650.112.760.4845.540.397F606W21.860.070.380.021.600.08...............25.560.22F814W21.860.060.380.011.580.06...............29.470.178F606W19.870.030.290.011.210.032.220.089.380.350.890.020.420.011.790.0439.050.38F814W19.310.030.270.011.130.031.950.068.240.270.860.020.390.011.630.0343.730.4310F606W20.230.040.490.022.050.076.190.7926.103.331.110.060.920.063.860.2541.730.25F814W20.360.050.650.022.730.105.110.5121.572.150.900.050.970.054.080.2146.590.3411F606W20.070.030.610.012.580.064.500.2218.960.910.870.020.880.023.720.1044.130.39F814W19.310.030.590.022.490.074.240.2017.880.840.860.020.840.023.550.0949.360.5712F606W20.340.020.220.000.910.022.000.068.420.270.970.020.350.011.470.0325.010.15F814W19.850.020.220.000.950.021.830.057.740.220.910.020.340.011.440.0328.480.1713F606W18.980.030.210.010.900.032.280.089.600.321.030.020.370.011.560.0340.740.38F814W18.520.020.220.000.930.022.020.078.500.290.960.020.350.011.490.0346.600.5014F606W18.920.020.440.011.840.045.030.2221.200.941.060.020.780.023.300.0824.960.29F814W19.260.030.480.012.010.055.850.4324.671.811.090.030.880.033.720.14183.600.2917F606W20.840.030.540.022.290.083.990.2216.850.940.870.030.780.033.300.1123.810.22F814W...0.700.032.950.123.310.0813.980.340.680.020.810.023.440.08181.310.3018F606W18.360.030.150.010.640.032.460.1010.390.421.210.030.320.011.350.0427.360.41F814W18.770.030.180.010.760.032.080.068.770.271.060.020.320.011.360.04185.030.4019F606W18.630.010.190.000.790.024.660.4519.631.911.390.040.490.022.060.1045.800.28F814W18.110.020.200.000.860.024.030.3316.981.381.300.040.470.022.000.0851.760.3622F606W18.840.010.510.002.160.025.460.1723.050.701.030.010.890.013.740.0645.290.28F814W18.060.010.540.012.270.035.310.1522.390.630.990.010.890.013.780.0652.700.3923F606W20.830.050.690.022.930.108.941.7337.707.281.110.091.310.125.540.5226.960.25F814W22.590.520.690.032.900.127.881.5533.236.551.060.091.230.125.190.50186.060.3124F606W20.560.040.390.011.650.068.051.9133.968.051.310.100.930.113.920.4545.310.20F814W20.570.070.340.021.410.07...............49.340.35

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) 25F606W19.100.020.570.022.420.075.150.1521.730.650.950.020.910.023.840.0844.100.25F814W18.750.030.610.022.570.084.900.1520.650.640.900.020.920.023.870.0948.340.2826F606W20.170.060.380.031.610.1010.515.7844.3124.371.440.241.040.284.411.1731.220.46F814W20.030.070.460.021.920.103.270.3613.791.530.860.050.650.042.740.1733.640.5727F606W18.540.010.370.001.550.024.810.1620.280.661.120.010.700.012.960.0524.750.27F814W18.050.010.380.011.620.034.390.1218.510.521.060.010.690.012.900.05184.130.3328F606W20.820.070.610.032.570.135.260.8622.183.640.940.070.950.084.010.3330.840.38F814W17.820.060.100.000.410.02...............37.400.7529F606W19.920.050.430.021.810.075.070.7721.403.241.070.070.780.063.290.2559.850.47F814W16.430.050.240.011.010.04...............725.3310.6930F606W18.760.010.300.011.270.034.190.1417.660.601.140.020.590.012.500.0543.630.22F814W18.350.020.310.011.310.033.080.0712.970.281.000.010.520.012.180.0447.550.2831F606W19.430.030.290.011.240.032.970.1712.540.741.000.030.500.022.090.0730.160.44F814W18.840.030.310.011.320.042.930.1912.360.810.970.030.510.022.140.0835.840.6232F606W19.950.020.330.011.400.04...............35.830.39F814W19.530.040.450.011.910.064.240.5017.892.110.970.050.730.043.100.1843.640.6033F606W17.930.040.200.010.850.033.330.1414.040.581.220.020.430.011.820.0531.850.43F814W15.940.050.070.000.290.013.690.3615.561.531.720.040.260.011.110.0537.200.3934F606W20.651.150.040.040.170.160.370.341.541.450.960.590.060.040.270.1939.033.73F814W19.600.530.040.030.190.120.510.272.151.131.060.360.080.030.330.1448.412.1935F606W19.840.030.370.011.560.043.820.3616.101.521.010.040.630.032.650.1360.590.47F814W16.550.030.270.011.130.032.710.2511.411.051.000.040.450.021.910.09722.076.7636F606W18.080.050.210.010.870.032.720.1111.470.481.120.030.400.011.670.0563.570.62F814W14.240.050.100.000.430.012.490.1910.490.811.390.040.260.011.110.04757.716.7837F606W20.810.080.710.033.020.145.180.6321.852.650.860.061.020.064.320.2761.300.51F814W17.790.081.070.064.530.253.710.1415.660.600.540.031.070.044.530.15695.638.8538F606W17.580.020.230.010.970.039.251.4439.016.091.600.070.760.063.190.2529.500.40F814W17.370.010.280.011.160.054.160.2217.540.921.180.030.560.022.380.0834.840.6540F606W19.980.040.440.011.850.062.710.1311.410.530.790.030.580.022.450.0761.120.75F814W16.710.040.430.011.800.062.120.068.960.270.700.020.510.012.150.05696.3510.2841F606W19.990.030.530.022.230.075.440.4922.942.081.010.040.900.043.790.1831.760.31F814W20.000.050.700.032.960.115.050.5021.302.130.860.051.000.054.220.2239.550.4743F606W19.140.030.350.011.490.043.480.1814.690.760.990.030.590.022.480.0766.650.58F814W16.250.030.400.011.690.052.530.0910.680.400.800.020.540.012.260.05814.969.8244F606W19.480.050.220.010.910.05...............75.610.77F814W16.870.060.190.010.820.03...............922.228.9145F606W20.660.030.530.022.240.072.580.0710.880.300.690.020.630.012.640.0628.610.42F814W20.110.040.590.022.490.092.570.0710.830.310.640.020.660.022.780.0735.770.5946F606W21.350.060.360.021.530.073.100.3513.061.460.930.050.560.032.370.1450.510.28

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) F814W21.140.080.500.032.110.102.480.1210.480.510.690.030.600.022.520.0953.120.4447F606W21.230.070.450.021.910.094.890.9020.633.791.030.080.790.073.320.3132.300.19F814W21.190.090.470.021.970.104.160.6517.562.720.950.070.740.063.120.2536.110.2548F606W20.170.030.370.011.550.052.290.109.640.430.790.020.490.012.060.0537.840.60F814W19.690.040.370.011.570.052.460.1710.390.720.820.030.510.022.150.0843.900.7149F606W18.240.050.120.000.520.022.040.118.600.451.220.030.260.011.110.0428.300.49F814W16.490.050.070.000.280.011.710.077.220.291.410.020.180.000.740.0232.770.5151F606W18.280.010.330.011.400.033.930.1716.590.701.070.020.600.012.550.0645.120.59F814W18.030.020.380.011.580.043.620.1715.290.740.990.020.620.022.610.0752.020.8353F606W19.380.020.430.011.810.042.480.0510.460.220.760.010.550.012.320.0468.780.67F814W16.070.030.390.011.640.042.040.048.600.190.720.010.480.012.010.03805.1810.0154F606W17.030.020.110.000.450.011.900.048.000.181.250.010.240.001.000.0124.390.53F814W16.560.030.100.000.420.011.760.057.420.201.250.010.220.000.930.0129.520.5955F606W17.690.010.240.011.020.033.410.1214.380.511.150.020.480.012.020.0434.150.62F814W17.500.020.260.011.110.033.120.1413.160.571.070.020.480.012.020.0539.750.8956F606W18.720.030.210.010.890.032.370.1010.010.431.050.030.380.011.580.0528.600.55F814W19.460.030.490.022.080.102.030.068.560.250.610.020.540.022.270.0730.330.7457F606W20.220.050.360.011.510.062.770.2711.701.140.890.050.530.032.240.1250.560.70F814W19.910.070.440.021.860.081.850.097.810.360.620.030.480.012.040.0654.081.2858F606W19.920.030.330.011.400.052.430.1310.250.530.860.030.480.022.020.0630.140.60F814W19.720.040.420.011.750.062.140.099.040.390.710.020.500.012.130.0634.150.7160F606W17.620.060.160.010.680.033.450.2114.560.871.330.030.390.011.650.0630.980.50F814W19.050.050.510.032.140.102.860.0912.080.390.750.030.640.022.720.0833.630.8162F606W16.900.010.130.000.540.004.150.2217.490.931.510.020.380.011.600.0451.300.37F814W16.960.020.160.000.660.014.640.4419.581.841.470.040.440.021.870.0960.770.4563F606W18.130.050.220.010.940.032.990.1312.620.531.130.020.430.011.820.0576.230.59F814W15.220.040.210.010.870.032.920.2012.300.831.150.030.410.021.720.07948.157.7964F606W18.350.030.240.011.010.03...............35.570.71F814W17.360.020.160.000.650.02...............41.770.7265F606W18.730.020.320.011.330.039.712.0540.958.651.490.090.910.093.850.3994.520.57F814W15.810.030.350.011.460.038.522.0035.938.441.390.100.900.103.790.431158.909.0266F606W19.920.040.660.022.800.082.760.0811.660.330.620.020.730.013.060.0687.130.88F814W16.720.060.450.021.890.082.320.129.780.520.710.030.550.022.300.081128.9014.8767F606W20.220.040.520.022.190.072.820.1111.900.460.740.020.650.022.730.0754.030.61F814W19.250.030.540.022.270.072.460.0710.370.280.660.020.620.012.600.0558.740.8868F606W19.530.040.280.011.160.053.500.4914.752.081.100.060.520.042.190.1694.970.72F814W16.770.050.350.011.460.062.200.149.280.600.800.030.470.021.960.081131.2614.3469F606W19.840.030.250.011.070.032.550.0710.750.291.000.020.430.011.790.0428.160.16F814W19.740.030.290.011.240.042.350.079.920.280.900.020.440.011.860.0432.080.19

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) 70F606W17.500.040.080.000.330.017.622.7232.1611.471.990.160.400.071.670.2956.970.36F814W18.690.040.220.010.930.032.090.128.790.490.980.030.360.011.510.0568.300.7271F606W17.980.030.220.010.930.033.670.1515.480.631.220.020.470.012.000.0553.390.46F814W16.900.030.080.000.330.01...............64.890.4772F606W18.530.020.350.011.460.034.820.3620.311.521.140.030.680.032.870.1190.110.64F814W15.550.020.430.011.800.043.050.1212.860.490.850.020.610.012.560.051106.7112.4673F606W19.020.040.280.011.160.053.540.3514.921.481.110.050.520.032.200.1294.440.74F814W16.990.080.450.031.900.123.330.3714.041.550.870.050.650.042.750.171148.5213.6875F606W20.410.040.380.011.620.062.620.1611.050.660.830.030.530.022.250.0853.930.57F814W20.520.070.490.022.080.092.080.098.780.370.630.030.540.022.290.0761.570.7876F606W18.870.050.160.000.680.02...............57.940.58F814W17.330.070.100.000.430.02...............69.580.7477F606W21.460.040.530.022.240.072.650.0811.190.350.700.020.640.012.680.0628.960.17F814W21.210.040.700.022.940.092.370.0610.010.250.530.020.690.012.910.0632.260.2078F606W18.190.020.250.001.080.027.460.9631.474.061.470.060.720.053.040.1951.690.36F814W17.360.020.230.000.980.025.620.5623.712.371.380.040.600.032.520.1261.170.4779F606W17.960.030.170.000.730.022.200.109.300.441.110.020.320.011.370.0467.750.95F814W17.070.020.140.000.570.011.520.066.410.251.050.020.240.001.010.0285.341.6280F606W17.730.030.260.011.110.0314.292.7160.2611.431.730.081.000.094.240.3954.460.40F814W16.910.040.210.010.890.0311.712.3449.379.861.740.090.810.083.440.3366.110.5781F606W17.690.010.380.001.610.028.430.6935.562.891.350.040.940.043.960.1673.150.63F814W16.730.010.370.011.560.0310.151.2442.795.211.440.051.010.064.270.2596.671.2982F606W19.890.020.290.011.240.033.310.1713.970.731.050.030.520.012.200.0633.930.22F814W19.510.020.290.011.240.033.140.1913.260.821.030.030.510.022.140.0738.840.2683F606W17.530.040.080.000.320.012.790.1411.750.601.570.030.240.011.000.0331.940.16F814W15.140.060.040.000.150.002.520.0810.630.331.850.020.160.000.650.0136.330.1884F606W17.630.030.300.011.270.043.260.1513.760.621.030.020.520.012.210.06106.141.53F814W17.440.020.350.011.490.042.650.1111.190.460.880.020.510.012.170.05126.112.3086F606W15.310.020.130.000.540.017.190.5530.332.321.750.030.500.022.090.0890.370.79F814W15.070.020.120.000.510.014.880.2720.601.141.600.030.400.011.690.05108.411.0487F606W16.100.030.300.011.260.038.240.6634.772.781.440.040.820.033.460.1499.901.32F814W15.200.030.260.011.080.038.410.8735.463.671.510.050.770.043.230.17130.651.6788F606W17.600.040.190.010.790.0315.848.4466.8235.611.930.230.880.233.730.9667.460.90F814W16.550.060.110.000.450.02...............96.511.1389F606W18.930.050.170.000.700.02...............60.100.46F814W18.690.050.170.010.730.03...............72.000.8892F606W19.440.020.200.000.830.02...............57.540.50F814W19.770.050.230.010.970.04...............65.670.6193F606W19.050.030.190.010.810.031.520.046.410.190.900.020.290.011.210.0372.320.78

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) F814W18.760.030.230.010.990.031.230.035.200.130.720.020.290.011.210.0393.261.2494F606W17.130.020.090.000.390.01...............60.860.73F814W16.350.020.080.000.330.014.450.6318.772.671.750.060.310.021.290.0973.150.5395F606W19.100.030.550.012.300.052.890.0912.210.380.720.020.670.012.830.06107.431.31F814W17.270.050.160.010.680.034.661.0719.684.511.470.100.450.051.900.21157.271.6396F606W20.340.040.380.011.620.052.800.1911.820.820.860.030.550.022.330.0975.580.58F814W19.680.060.450.021.900.072.910.2212.260.950.810.040.610.032.570.11103.430.9898F606W20.930.080.460.021.920.09...............57.780.56F814W21.050.070.540.022.270.10...............66.210.4799F606W18.120.020.200.010.860.032.960.2412.491.021.160.040.410.021.730.07126.341.05F814W17.530.030.140.010.570.032.910.5612.292.361.330.090.330.031.390.13168.881.46100F606W19.240.030.170.010.730.037.052.8429.7511.971.610.170.570.112.420.4758.850.37F814W16.040.080.050.000.210.01...............67.090.52101F606W18.940.020.460.011.950.053.290.0713.890.300.850.010.660.012.770.0554.360.53F814W18.780.020.550.022.300.072.900.0712.230.280.730.020.670.012.830.0563.210.72102F606W19.520.030.300.011.280.052.380.1310.030.550.890.030.450.011.900.0692.790.85F814W19.010.040.370.021.580.071.960.078.280.290.720.030.460.011.930.06120.851.43103F606W18.740.030.440.011.850.055.160.3121.751.321.070.030.790.033.350.1161.650.48F814W18.550.030.470.011.990.065.720.6324.142.641.080.050.870.053.660.2075.590.62104F606W19.540.030.310.011.320.053.900.4216.461.781.090.050.580.032.470.1484.870.48F814W18.680.030.380.011.620.062.300.079.710.310.780.020.500.012.120.05108.111.13105F606W17.950.030.200.010.830.032.110.098.920.401.030.020.340.011.440.04121.611.39F814W18.550.040.370.011.560.051.450.036.120.140.600.020.390.011.660.04146.052.56109F606W17.630.060.090.000.360.01...............174.580.90F814W18.670.080.350.021.460.083.210.4713.541.970.970.070.560.042.360.18231.152.06110F606W18.320.020.200.000.830.022.970.2412.521.031.180.040.400.021.690.0790.460.80F814W17.990.020.210.000.870.022.110.158.890.641.010.030.350.011.480.05118.601.46114F606W15.610.030.060.000.240.002.070.078.740.291.570.020.180.000.750.0184.360.71F814W14.660.040.050.000.220.001.780.057.510.191.540.010.160.000.660.01106.811.02116F606W20.950.140.520.022.190.08...............244.032.18F814W20.570.200.090.010.400.030.120.010.520.030.120.050.060.000.250.01221.412.69117F606W18.170.030.200.000.860.02...............220.131.57F814W18.350.070.270.011.130.06...............281.462.69118F606W19.320.050.690.032.900.113.450.1514.570.620.700.030.820.023.470.10182.362.27F814W17.940.040.370.011.570.062.900.2212.220.920.890.040.550.022.320.10266.502.87120F606W19.310.020.190.000.780.02...............81.110.49F814W18.890.030.170.000.740.02...............107.240.90121F606W19.740.030.280.011.160.03...............57.480.42F814W19.570.040.380.011.620.064.700.6619.832.771.090.060.710.053.000.2166.670.40

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) 122F606W18.610.010.400.011.700.034.340.1618.290.691.030.020.700.012.950.0674.430.47F814W18.170.020.470.011.990.043.620.1215.280.490.880.020.690.012.930.0596.740.86124F606W18.420.020.160.000.690.024.410.6318.612.681.430.060.440.031.870.1376.920.41F814W17.570.020.110.000.480.016.872.5728.9610.851.780.160.460.081.920.34103.240.69125F606W19.230.020.260.001.100.021.620.036.850.110.790.010.350.001.470.0267.550.54F814W18.630.020.270.011.120.031.470.036.180.110.740.010.330.001.410.0295.520.87126F606W17.510.020.180.000.750.013.060.1112.900.481.240.020.390.011.630.0370.950.54F814W17.020.020.190.000.810.022.410.0810.180.331.100.020.360.011.520.0396.711.07127F606W20.700.060.420.021.780.091.940.088.190.340.660.030.490.022.050.0770.200.80F814W19.550.050.290.011.240.051.440.066.060.260.690.030.350.011.460.0494.721.35128F606W18.630.030.220.010.910.032.660.1811.240.751.090.030.400.011.690.0687.060.75F814W17.950.030.200.010.860.031.940.108.200.440.980.030.330.011.400.04113.521.39129F606W18.810.020.280.001.160.022.750.1111.600.481.000.020.460.011.940.0469.810.49F814W18.440.020.310.011.310.032.560.1210.790.500.920.020.470.012.000.0593.310.82131F606W19.470.030.270.011.140.031.900.068.010.250.850.020.380.011.610.0473.690.71F814W18.850.030.250.011.050.041.370.035.760.140.740.020.310.011.310.03101.131.30132F606W19.720.050.340.011.450.054.870.8920.533.751.150.080.680.062.880.26125.720.75F814W19.030.050.390.021.640.073.510.3614.791.530.950.050.620.032.610.14141.181.18133F606W19.270.020.380.011.610.052.170.059.140.230.750.020.490.012.050.0487.970.92F814W18.450.030.420.011.780.061.900.048.010.170.650.020.480.012.020.04107.781.48134F606W18.350.020.360.011.510.036.900.9929.094.191.280.060.820.063.480.24127.651.01F814W18.260.030.400.011.670.054.960.6820.922.861.100.060.740.053.120.21146.761.33135F606W18.930.040.300.011.280.064.370.7118.433.011.160.070.610.052.560.21127.440.99F814W18.240.040.250.011.070.053.120.4013.161.681.090.060.470.031.980.13144.281.30136F606W18.490.030.190.010.800.039.885.2141.6721.991.720.230.710.182.980.76140.120.87F814W18.250.040.250.011.050.045.581.6023.546.751.350.120.620.092.610.36158.080.88137F606W18.380.020.190.010.810.033.710.4015.651.701.290.050.440.031.860.1085.560.61F814W17.290.020.180.010.770.032.300.109.690.411.100.020.340.011.440.04115.371.20139F606W16.290.010.180.000.740.023.460.1314.610.561.290.020.410.011.730.04136.041.41F814W15.540.030.140.000.610.022.720.0911.460.391.280.020.330.011.380.03152.491.81140F606W18.830.020.340.011.430.03...............103.931.35F814W17.980.030.310.011.330.03...............126.161.81141F606W19.820.040.470.011.980.063.660.3015.451.270.890.040.700.032.940.12107.230.75F814W19.480.050.630.022.640.094.420.3818.641.590.850.040.890.043.740.17121.720.93142F606W18.970.030.200.010.860.031.930.138.130.530.980.030.330.011.400.05134.701.04F814W18.690.040.230.010.990.031.490.066.270.270.800.020.310.011.330.04138.141.45146F606W15.460.020.140.000.580.017.600.9332.063.921.740.050.530.032.230.13143.951.27F814W14.830.020.130.000.530.015.080.4121.411.731.610.040.410.021.750.07158.931.16147F606W19.300.020.310.011.320.03...............85.750.62

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IdaFilter0RcRcRtRtcRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(arcsec)(pc)(Lpc2) F814W19.390.060.490.022.050.097.392.1031.168.861.180.121.000.144.210.58101.010.73148F606W19.900.050.320.011.360.052.760.2311.660.980.930.040.500.022.120.10113.930.76F814W19.140.060.260.011.110.053.550.7514.983.161.130.090.510.052.150.22134.540.92149F606W18.550.020.250.001.050.027.391.2531.195.281.470.070.710.062.980.2483.430.46F814W17.700.020.290.011.210.034.030.2817.001.181.150.030.570.022.390.0998.530.70150F606W17.090.020.140.000.610.0110.141.6642.777.011.850.070.620.052.640.21143.580.27F814W16.750.030.140.000.610.027.411.0731.244.521.710.060.540.042.260.16166.130.29151F606W20.240.050.450.021.900.083.350.2614.141.080.870.040.650.032.760.1298.610.68F814W20.170.080.650.032.740.122.390.0810.060.350.560.020.670.022.820.08110.491.19153F606W19.220.050.210.010.890.033.750.2915.821.241.250.040.470.021.980.08144.150.27F814W17.260.060.110.000.460.022.790.1411.780.611.400.030.290.011.220.04165.540.32154F606W19.370.020.660.012.780.055.480.2423.131.020.920.021.010.024.260.1069.760.43F814W19.140.030.880.023.730.094.660.1519.660.640.720.021.090.024.580.0980.320.71156F606W20.090.040.260.011.100.033.180.2213.400.921.090.030.480.022.030.07139.570.25F814W20.430.060.300.011.270.042.880.2112.170.890.980.040.490.022.080.08160.840.33157F606W16.920.010.140.000.590.013.950.1516.660.621.450.020.390.011.630.04141.790.35F814W16.610.010.150.000.620.013.340.1114.100.461.360.020.370.011.540.03162.490.46158F606W20.340.040.350.011.480.033.130.1713.190.720.950.030.560.022.340.07143.720.31F814W19.590.040.260.011.080.035.371.1222.654.701.320.090.620.062.590.26165.990.32159F606W19.150.030.430.011.810.053.690.1015.590.430.940.020.670.012.820.06141.550.32F814W15.550.050.110.000.470.013.110.0913.120.391.450.020.310.011.290.03166.320.40161F606W22.250.120.490.012.050.064.320.2718.231.140.950.030.770.033.250.11134.430.16F814W22.890.370.590.022.510.093.880.1816.390.770.820.030.810.023.410.10155.290.23 2

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 1F606W19.630.020.390.031.660.114.560.380.330.041.410.1636.760.22F814W18.940.020.350.021.480.094.160.300.330.041.400.1641.900.252F606W19.140.020.080.000.320.021.650.060.080.000.320.0236.740.29F814W18.920.020.070.000.290.021.290.040.060.000.270.0239.990.403F606W22.260.051.190.235.000.985.131.470.890.293.741.2237.890.26F814W21.000.040.280.031.180.141.810.210.280.031.180.1441.910.424F606W18.330.020.130.010.540.032.760.100.290.051.240.2137.220.19F814W18.360.020.140.010.610.032.790.120.310.061.330.2543.670.265F606W20.580.030.120.010.510.041.310.080.110.010.470.0441.200.40F814W20.730.040.210.030.880.102.060.25......49.670.506F606W19.540.020.250.011.080.052.500.130.980.414.141.7340.160.32F814W19.040.030.230.010.970.062.230.12......45.230.417F606W21.840.050.320.031.370.111.770.120.320.031.370.1125.280.19F814W21.760.050.270.021.150.101.470.100.260.021.100.0928.930.228F606W20.230.020.560.062.380.276.040.980.360.061.520.2441.320.26F814W19.700.030.550.072.330.316.551.280.330.061.390.2546.550.3010F606W20.460.020.690.052.890.233.360.300.910.193.850.8042.040.27F814W20.800.011.150.174.840.735.411.230.810.203.430.8447.470.3511F606W20.470.011.340.135.640.537.241.050.740.093.100.3946.080.31F814W19.720.011.390.155.860.638.191.390.700.092.940.4052.480.4412F606W20.660.010.490.062.080.256.541.080.290.051.240.1926.120.10F814W20.210.010.630.112.670.459.342.430.290.061.220.2429.790.1213F606W19.230.030.330.021.410.103.990.320.340.041.420.1943.260.30F814W18.810.020.370.031.570.134.600.500.310.051.310.1949.830.4014F606W19.130.020.790.063.320.254.420.390.690.092.910.3626.030.30F814W19.550.010.810.063.400.254.130.360.770.103.260.44184.380.3117F606W21.250.020.960.104.060.445.370.850.690.122.890.5024.600.20F814W.....................18F606W18.560.030.500.052.120.196.770.750.290.031.230.1329.730.26F814W19.090.030.710.093.000.3610.531.920.300.041.260.17187.800.27

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 19F606W18.760.010.250.011.040.042.710.090.600.112.540.4546.140.30F814W18.270.020.290.011.210.052.990.130.500.072.100.3052.590.3822F606W19.080.000.770.023.270.093.780.130.840.053.550.2246.770.30F814W18.310.000.830.033.480.113.940.160.840.053.560.2354.900.4323F606W21.030.020.750.063.180.242.470.19......26.540.31F814W20.130.250.690.062.910.272.300.22......185.260.4424F606W20.700.020.510.042.160.162.880.231.000.304.221.2845.430.21F814W20.590.040.350.031.500.132.130.17......49.400.2825F606W19.410.030.930.063.920.244.190.280.880.093.690.3845.020.26F814W19.110.030.970.074.080.294.260.340.890.113.750.4549.210.3226F606W20.320.050.560.082.350.323.050.430.920.393.871.6531.550.44F814W.....................27F606W18.720.010.460.011.940.052.910.080.870.083.660.3425.100.31F814W18.290.010.500.012.130.063.150.090.770.063.260.28184.930.3828F606W21.150.010.700.082.970.352.900.431.350.695.692.9330.840.44F814W17.800.070.080.010.350.041.830.110.080.010.350.0436.820.5929F606W20.150.030.450.041.890.162.420.21......59.290.60F814W16.450.030.220.020.910.081.850.140.220.020.910.08713.049.3830F606W18.940.010.800.053.390.236.180.520.500.042.120.1845.220.19F814W18.610.021.010.094.270.409.251.270.470.051.960.2150.180.2431F606W19.700.020.650.082.760.326.251.010.410.061.710.2732.040.31F814W19.120.021.761.047.424.39.........38.390.4532F606W19.960.020.360.031.510.122.160.16......36.100.44F814W19.830.010.600.062.550.263.420.460.780.223.280.9344.490.6633F606W18.100.040.280.011.180.063.080.130.450.061.920.2733.590.38F814W15.970.050.070.000.300.022.170.06......36.280.4734F606W19.630.060.160.020.690.071.200.070.150.010.620.0631.831.13F814W18.840.060.090.010.400.051.110.070.080.010.350.0438.751.2835F606W20.110.010.420.031.760.122.750.230.970.364.091.5261.060.49F814W16.830.020.320.031.370.132.990.360.560.212.380.89734.286.19

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 36F606W18.300.060.280.021.190.083.180.190.420.071.770.3065.910.59F814W14.340.050.120.010.530.042.610.140.370.141.570.61764.677.3137F606W21.320.040.930.123.940.493.550.611.120.374.741.5761.760.56F814W.....................38F606W17.660.020.310.021.320.082.580.090.980.274.151.1429.220.41F814W17.560.010.850.073.600.296.410.630.520.052.190.2137.690.5440F606W20.490.020.900.173.810.707.342.130.490.122.080.5164.540.46F814W17.380.031.360.435.721.8116.579.350.430.151.800.63762.996.4941F606W20.230.020.600.052.530.192.730.221.430.546.012.2931.450.41F814W20.410.020.870.123.680.493.330.601.180.484.992.0339.880.5643F606W19.440.020.630.052.670.204.680.460.520.072.200.2869.260.48F814W16.720.020.760.093.210.386.371.160.470.081.960.34868.887.6244F606W19.460.040.180.020.760.071.800.120.180.020.760.0774.650.71F814W16.860.050.170.020.730.081.800.170.170.020.730.08916.019.5845F606W.....................F814W.....................46F606W21.860.020.690.122.920.495.691.410.470.121.970.5051.110.22F814W.....................47F606W21.510.040.710.102.990.43.........32.520.18F814W21.650.051.330.375.611.5511.205.240.540.172.260.7436.710.1948F606W20.670.010.860.143.630.578.812.270.410.081.720.3440.830.41F814W20.140.010.510.062.140.263.900.650.530.142.220.6045.870.5549F606W18.420.060.170.010.700.052.950.160.300.061.270.2630.290.34F814W16.660.050.090.000.370.022.710.080.220.040.920.1835.150.4351F606W18.500.010.540.032.300.123.890.230.570.062.390.2447.610.57F814W18.300.010.630.042.680.184.420.360.560.062.360.2755.590.8353F606W19.930.021.270.235.360.9913.744.410.450.091.900.4075.530.37F814W16.640.030.980.194.140.7911.373.690.390.091.650.37901.985.5654F606W17.220.020.190.010.800.033.750.150.210.020.880.0729.670.39F814W16.750.030.190.010.800.054.050.230.190.020.790.0834.670.50

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 55F606W17.870.010.520.042.180.164.690.370.420.051.790.1937.530.51F814W17.720.010.830.113.490.468.071.510.420.061.770.2744.390.6756F606W19.000.030.400.041.680.184.480.560.340.061.450.2531.240.41F814W.....................57F606W20.610.030.640.122.720.515.471.540.450.141.900.5752.220.55F814W.....................58F606W20.340.031.150.434.861.81.........32.970.38F814W20.330.031.080.504.552.10.........37.640.4860F606W17.760.060.270.021.140.083.410.200.350.051.470.2232.780.47F814W.....................62F606W17.000.010.160.000.690.012.620.040.470.041.990.1952.350.36F814W17.060.020.200.010.850.032.630.090.570.122.400.4960.880.4963F606W18.370.050.430.031.820.144.400.350.380.051.610.1979.320.45F814W15.430.050.270.021.130.092.930.180.500.122.090.50965.616.7664F606W18.370.030.250.011.050.052.110.08......35.310.51F814W17.370.020.140.010.600.031.900.070.140.010.600.0340.740.6265F606W18.800.000.320.011.350.052.150.07......93.380.61F814W15.910.010.350.011.490.062.180.09......1144.3910.0066F606W20.810.031.100.224.620.946.602.160.650.192.740.8192.830.63F814W17.390.050.600.092.520.394.210.930.560.182.360.751177.7111.2167F606W20.830.020.840.123.540.495.381.110.600.132.520.5656.920.47F814W19.950.021.570.606.602.5415.2110.360.520.222.200.9564.930.6068F606W19.790.030.370.041.540.153.120.340.570.172.410.7395.960.66F814W.....................69F606W20.160.030.620.052.610.226.280.660.380.041.620.1729.360.12F814W20.130.040.590.052.490.225.690.630.400.051.680.2033.390.1470F606W17.540.050.080.010.350.032.150.08......56.700.38F814W18.970.040.270.021.130.103.100.280.430.121.800.4870.820.5571F606W18.140.030.460.031.920.114.320.260.410.041.740.1656.080.38F814W16.780.030.060.000.250.011.700.030.060.000.250.0162.140.58

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 72F606W18.740.020.470.031.990.103.090.170.750.123.180.5191.310.65F814W15.930.010.710.063.010.254.870.550.560.082.370.321167.8810.0473F606W19.240.040.500.062.130.244.390.570.450.081.880.3596.350.58F814W.....................75F606W.....................F814W.....................76F606W18.830.050.140.010.600.041.850.070.140.010.600.0457.320.50F814W17.340.070.100.010.420.032.010.08......69.070.6877F606W.....................F814W.....................78F606W18.270.020.280.011.200.052.340.072.151.169.074.9150.910.41F814W17.460.020.280.011.160.052.500.091.050.324.441.3460.240.5579F606W18.200.030.260.021.090.073.620.240.300.041.270.1772.850.68F814W17.330.020.210.010.880.053.740.240.230.030.970.1295.851.1480F606W17.780.030.290.011.230.052.240.05......53.690.35F814W16.960.040.230.010.990.052.230.06......65.180.5481F606W17.800.010.420.011.760.042.360.052.890.9312.203.9171.400.72F814W16.830.010.400.011.700.052.310.053.781.7615.937.4294.001.3682F606W20.140.020.520.042.190.154.490.380.450.051.890.2235.060.21F814W19.770.020.480.032.010.144.180.380.450.061.890.2639.880.2583F606W17.700.030.130.000.550.023.070.080.210.020.900.0832.710.15F814W15.500.050.080.000.330.013.030.050.130.010.560.0537.720.1784F606W17.880.030.710.092.990.376.141.000.450.071.880.30113.681.10F814W17.800.010.830.143.520.597.561.910.440.091.870.40137.371.4986F606W15.380.020.160.000.660.022.370.031.000.244.231.0189.040.84F814W15.140.020.140.000.600.022.390.030.830.193.500.81107.371.1787F606W16.190.030.400.021.680.072.730.080.940.143.970.6198.981.52F814W15.290.030.340.021.430.072.650.090.930.203.930.84128.981.8288F606W17.650.040.210.010.870.052.210.08......67.180.71F814W16.310.070.060.000.270.021.520.050.060.000.260.0290.161.42

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 89F606W18.870.050.140.010.570.041.730.080.140.010.570.0458.970.55F814W18.700.050.160.010.660.061.870.130.160.010.660.0671.080.7292F606W19.420.020.160.010.670.051.700.090.160.010.660.0556.840.44F814W19.790.020.270.021.130.102.330.20......66.020.4493F606W19.450.031.010.404.271.70.........78.770.42F814W.....................94F606W17.180.020.120.010.520.032.410.070.650.262.751.1061.580.41F814W16.460.020.130.010.540.032.870.080.250.031.080.1474.440.5495F606W19.690.020.890.093.740.365.510.800.620.092.600.40114.981.02F814W17.320.050.150.010.620.042.030.10......153.741.9396F606W20.820.010.560.062.380.254.180.610.530.112.240.4777.300.49F814W20.290.020.870.193.680.796.842.400.500.162.120.66106.400.7898F606W20.980.020.510.042.140.192.320.22......58.000.41F814W21.050.040.500.052.110.221.830.200.500.052.100.2265.800.6299F606W18.320.020.280.021.190.073.190.20......128.930.98F814W17.630.030.130.010.560.042.200.13......168.391.59100F606W19.320.020.200.020.840.072.350.14......58.800.39F814W15.810.150.030.000.140.021.720.050.030.000.130.0265.800.53101F606W19.350.011.610.306.801.2713.104.020.590.122.480.5158.760.40F814W.....................102F606W19.820.030.230.020.960.082.230.16......95.130.64F814W.....................103F606W18.970.030.610.042.550.153.240.190.870.133.660.5662.450.46F814W18.750.020.540.032.270.142.650.171.470.526.192.2075.090.74104F606W19.740.020.300.021.260.102.290.15......84.590.53F814W19.240.030.960.204.050.839.373.110.440.111.840.46115.040.80105F606W18.220.040.310.021.290.093.910.310.320.041.330.18129.310.95F814W.....................109F606W17.080.120.030.000.130.021.240.040.030.000.120.01164.851.39F814W19.010.070.380.051.590.232.680.410.970.774.083.24232.651.95

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 110F606W18.490.020.230.010.980.052.710.140.570.152.410.6392.070.70F814W18.250.010.220.010.940.062.650.190.620.242.601.03122.071.20114F606W15.880.030.130.010.550.033.710.150.150.010.620.0590.160.54F814W14.940.030.100.000.440.023.340.100.140.010.590.05116.700.77116F606W20.930.040.470.051.990.191.790.180.470.051.990.19242.412.09F814W.....................117F606W18.120.040.140.010.600.041.500.060.140.010.580.04213.501.70F814W18.380.050.290.031.210.112.160.18......281.842.17118F606W20.080.041.180.234.970.976.101.770.750.213.150.89192.191.32F814W18.320.020.440.041.840.193.080.360.700.232.950.99272.432.54120F606W19.220.020.130.010.530.031.520.050.120.010.520.0379.100.55F814W18.770.030.110.010.480.031.460.060.110.010.460.03104.250.90121F606W19.770.020.280.021.180.072.070.10......57.170.38F814W19.810.020.460.041.950.152.820.240.980.344.121.4266.770.44122F606W18.850.010.540.022.300.083.280.130.760.083.200.3176.340.43F814W18.540.010.850.063.600.265.240.520.620.072.630.30102.040.62124F606W18.520.030.180.010.750.042.340.091.380.935.823.9476.760.44F814W17.590.020.110.000.460.021.990.060.110.000.460.02102.030.73125F606W19.730.020.570.052.400.227.881.120.290.041.240.1574.680.36F814W19.200.020.480.042.010.196.460.900.290.041.210.16105.240.64126F606W17.680.020.260.011.110.043.240.100.380.031.590.1374.180.45F814W17.270.030.360.021.530.084.480.260.310.031.320.11105.080.79127F606W21.740.070.920.363.881.5210.026.770.400.201.680.8374.740.45F814W20.380.050.540.172.260.707.133.600.300.131.260.55101.730.74128F606W18.840.020.330.031.400.113.750.350.370.061.550.2689.680.55F814W18.240.030.360.041.510.164.850.680.280.051.190.20120.260.86129F606W19.060.010.320.011.360.052.870.130.630.112.680.4571.070.48F814W18.770.010.380.021.610.083.170.200.570.102.420.4196.100.70131F606W.....................F814W.....................

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 132F606W19.960.020.450.031.900.143.040.260.760.193.190.82126.530.81F814W19.420.030.650.072.750.294.560.640.550.102.330.43144.281.04133F606W.....................F814W.....................134F606W18.480.010.400.021.670.082.420.122.011.078.464.50126.571.20F814W18.470.010.420.031.780.122.460.181.871.297.875.46145.701.65135F606W19.150.030.420.041.760.163.120.300.650.182.760.76128.311.04F814W18.450.040.270.021.160.102.550.220.930.593.942.48144.961.34136F606W18.540.010.200.010.840.052.170.11......139.580.80F814W18.380.020.300.031.280.112.660.240.820.403.441.69158.320.95137F606W18.540.010.390.031.660.124.180.310.370.041.560.1887.340.52F814W17.530.020.380.031.620.124.970.430.300.031.250.13122.720.94139F606W16.430.010.430.031.790.104.700.290.350.031.470.12145.051.09F814W15.730.030.320.021.340.094.260.260.290.031.230.12164.351.48140F606W18.810.010.280.011.160.051.720.060.280.011.160.05100.871.10F814W17.870.010.150.010.630.031.260.030.140.000.580.02114.351.72141F606W20.230.020.610.052.570.223.460.390.770.183.240.76108.430.78F814W20.010.021.130.194.790.815.961.620.740.193.100.82124.400.88142F606W19.290.030.300.031.250.113.800.430.320.061.350.26138.360.82F814W19.210.040.430.081.820.326.021.570.280.071.170.30145.580.89146F606W15.560.020.270.011.140.043.190.080.400.031.700.14146.891.05F814W14.950.020.330.021.400.083.920.170.340.031.440.12162.401.16147F606W19.270.030.260.011.080.061.700.070.250.011.070.0684.080.72F814W19.570.030.490.042.080.192.250.20......99.770.92148F606W20.280.050.370.041.580.162.940.340.680.272.881.14115.300.67F814W19.360.040.260.031.120.112.290.24......134.091.08149F606W18.640.020.260.011.110.042.240.07......82.570.50F814W17.890.020.350.021.470.072.780.120.780.163.280.6598.880.77150F606W17.200.020.280.011.170.053.070.090.450.041.910.18144.180.25F814W17.000.030.280.011.200.063.110.110.450.051.880.22166.630.29

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IdaFilter0acacRhRhbk(magarsec2)(arcsec)(pc)(arcsec)(pc)(Lpc2) 151F606W20.750.050.600.072.510.283.550.490.710.193.020.82100.180.55F814W.....................153F606W19.400.060.300.021.260.083.090.170.480.082.020.33144.820.25F814W17.390.060.160.010.680.042.940.110.300.051.260.19166.680.30154F606W19.720.011.150.074.850.294.820.380.920.093.860.3771.640.39F814W.....................156F606W20.450.030.810.123.440.509.212.040.380.061.580.27140.580.19F814W21.160.060.870.173.650.719.653.000.390.091.630.38162.020.23157F606W17.040.010.310.011.290.053.840.120.320.021.370.09144.030.27F814W16.760.010.380.021.620.074.640.200.320.021.340.08165.880.33158F606W20.830.030.450.031.900.113.280.230.630.112.650.46144.460.31F814W19.720.040.240.011.020.062.090.10......165.110.40159F606W19.490.030.840.083.550.355.270.630.610.082.580.35143.270.25F814W15.690.050.190.010.800.033.170.090.280.031.200.11167.550.40161F606W27.8912.020.810.083.430.344.560.590.690.122.910.50134.920.15F814W..................... 2

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IzaskunSanRomanwasborninAlsasua,Spain,whereshegrewupformostofherlife.Sinceherearlyyearsshewasinterestedinastronomy,interestthatshecombinedwithherpassionformusic.HercuriosityaboutscienceandtheexplorationoftheUniversegrewupduringhersenioryearinhighschoolandshedecidedtopursueacareerinastronomy.IzaskunmovedtoTenerife,CanaryIslandswhereshereceivedherB.S.inphysicsandastrophysicsfromtheUniversityofLaLaguna.WhileatULL,shemettheloveofherlifeandactualhusband.ShethenmovedtoGainesville,FloridatobegingraduateschoolattheUniversityofFloridawheresheworkedonstellarpopulationontheLocalGroupwithProfessorAtaSarajedini.AfterreceivingherPh.D.,IzaskunwillmoveontoUniversidaddeConcepcion,Chile,toworkwithDrs.DougGeislerandSandroVillanova.Shehasnotgivenupherpassionformusicandstilldreamsofbecomingaprofessionalharpist,Inthemeantime,sheplaystheguitar. 323