Advanced Camera for Surveys Observations of Young Star Clusters in the Interacting Galaxy U

We present the first Advanced Camera for Surveys (ACS) observations of young star clusters in the colliding/merging galaxy UGC 10214. The observations were made as part of the Early Release Observation (ERO) program for the newly installed ACS during servi

ACCEPTED

FORPUBLICATIONIN

TheAstrophysicalJournal

APreprinttypesetusingLTEXstyleemulateapjv.11/12/01

ADVANCEDCAMERAFORSURVEYSOBSERVATIONSOFYOUNGSTARCLUSTERSINTHE

INTERACTINGGALAXYUGC10214

H.D.TRAN1,M.SIRIANNI1,H.C.FORD1,G.D.ILLINGWORTH2,M.CLAMPIN3,G.HARTIG3,R.H.

BECKER4,R.L.WHITE3,F.BARTKO5,N.BENÍTEZ1,J.P.BLAKESLEE1,R.BOUWENS2,T.J.

BROADHURST6,R.BROWN3,C.BURROWS3,E.CHENG7,N.CROSS1,P.D.FELDMAN1,M.FRANX8,D.A.GOLIMOWSKI1,C.GRONWALL9,L.INFANTE10,R.A.KIMBLE7,J.KRIST3,M.LESSER11,D.MAGEE2,A.

R.MARTEL1,WM.J.MCCANN1,G.R.MEURER1,G.MILEY8,M.POSTMAN3,P.ROSATI12,W.B.

SPARKS3,ANDZ.TSVETANOV1

Received2002October11;accepted2002November14

arXiv:astro-ph/0211371v1 15 Nov 2002

ABSTRACT

Wepresentthe rstAdvancedCameraforSurveys(ACS)observationsofyoungstarclustersinthecollid-ing/merginggalaxyUGC10214.TheobservationsweremadeaspartoftheEarlyReleaseObservation(ERO)programforthenewlyinstalledACSduringservicemissionSM3BfortheHubbleSpaceTelescope(HST).Manyyoungstarclusterscanbeidenti edinthetailsofUGC10214,withagesrangingfrom～3Myrto10Myr.TheextremeblueV I(F606W F814W)colorsofthestarclustersfoundinthetailofUGC10214canonlybeex-plainedifstrongemissionlinesareincludedwithayoungstellarpopulation.Thishasbeencon rmedbyourKeckspectroscopyofsomeofthesebrightbluestellarknots.ThemostluminousandlargestoftheseblueknotshasanabsolutemagnitudeofMV= 14.45,withahalf-lightradiusof161pc,andifitisasinglestarcluster,wouldqualifyasasuperstarcluster(SSC).Alternatively,itcouldbeasuperpositionofmultiplescaledOBassociationsorclusters.Withanestimatedageof～4-5Myr,itsderivedmassis<1.3×106M⊙.Thustheyoungstellarknotisunboundandwillnotevolveintoanormalglobularcluster.Thebrightblueclustersandassociationsaremuchyoungerthanthedynamicalageofthetail,providingstrongevidencethatstarformationoccursinthetaillongafteritwasejected.UGC10214providesanearbyexampleofprocessesthatcontributedtotheformationofhalosandintra-clustermediainthedistantandyoungerUniverse.

Subjectheadings:galaxies:individual(VV29,Arp188,UGC10214)–galaxies:starclusters

1.INTRODUCTION

In2002April,aspartoftheearlyreleaseobservations(EROs)todemonstratethenewcapabilitiesoftheAdvancedCameraforSurveys(ACS;Fordetal.1998)installedinearlyMarch2002ontheHubbleSpaceTelescope(HST),deepim-agesoftheinteractinggalaxiesNGC4676(“TheMice”)andUGC10214(“Tadpole”=VV29=Arp188)wereobtained,us-ingtheWideFieldChannel(WFC)withtheF475W(g),F606W(broadV)andF814W(I) lters.NGC4676isapairofgalax-iescaughtintheactofacollision,whileUGC10214appearsasadisturbedspiralwithalongtailofstars.Inthispaper,wepresenttheobservations,andfocusonthesearchandidenti -cationofveryyoungstarclustersfoundinthelongtidaltailofoneofthesegalaxies,UGC10214.Inaddition,wepresentop-ticalspectroscopyofsomeofthesebrightestclustersobtainedwiththeKeck10mtelescope.Adetailedanalysisofthedata,includingthemagnitudes,colors,speci cfrequenciesandspa-tialdistributionsofcandidateclustersfoundinthebothsys-12

temsofinteractinggalaxieswillbethesubjectofafuturepaper(Siriannietal.2002).Analysisofthenumerousfaintgalaxiesvisibleinthebackground eldwillalsobepresentedinasepa-ratepaper(Benítezetal.2002).TheredshiftofUGC10214isz=0.03136(Briggsetal.2001),placingitatadistanceof125Mpc(Ho=75kms 1Mpc 1).Atthisdistance,1′′correspondsto606pc,and1WFCpixelcovers30.3pc.

2.OBSERVATIONSANDREDUCTION

2.1.ACSImaging

TheinitialACSobservationsofUGC10214,dubbedtheTadpole,wereobtainedon2002April1(UT),usingtheACS/WFCthroughtheF475W(g),F606W(broadV)andF814W(I) lters.WeusedPOSTARGcommandoffsetsof3′′intheYdirectiontobridgethegapbetweenthetwoWFCchips.Inordertominimizethevisibilityofthegap,foreach lter,wecommandedthetelescopeoffsetstothreepointings,at

′′′′′′′′

(0′′,0′′),(0.248,3.001)and( 0.248, 3.001).AteachPOS

DepartmentofPhysicsandAstronomy,JohnsHopkinsUniversity,Baltimore,MD21218.

UCO/LickObservatory,UniversityofCalifornia,SantaCruz,CA95064.3STScI,3700SanMartinDrive,Baltimore,MD21218.

4PhysicsDepartment,UniversityofCalifornia,Davis,CA95616,andInstituteforGeophysicsandPlanetaryPhysics,L-413,LawrenceLivermoreNationalLabora-tory,7000EastAvenue,Livermore,CA94550.

5BartkoSci.&Tech.,P.O.Box670,Mead,CO80542-0670.

6TheRacahInstituteofPhysics,HebrewUniversity,Jerusalem91904,ISRAEL.7NASA-GSFC,Greenbelt,MD20771.

8LeidenObservatory,P.O.Box9513,2300Leiden,TheNetherlands.

9DepartmentofAstronomyandAstrophysics,ThePennsylvaniaStateUniversity,525DaveyLab,UniversityPark,PA16802.10Ponti ciaUniversidadCatolicadeChile,Santiago,Chile.

11StewardObservatory,UniversityofArizona,Tucson,AZ85721.

12EuropeanSouthernObservatory,Karl-Schwarzschild-Str.2,D-85748Garching,Germany.

1

第1页下一页