The galaxy populations from the centers to the infall regions in z~0.25 clusters

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Astronomy&Astrophysicsmanuscriptno.8735April17,2008

cESO2008

Thegalaxypopulationsfromthecenterstotheinfallregionsin

z≈0.25clusters

M.Verdugo1,B.L.Ziegler1,2,3 andB.Gerken4

1

arXiv:0709.4508v3 [astro-ph] 17 Apr 2008

234

Institutf¨urAstrophysikG¨ottingen,Georg-AugustUniversit¨atG¨ottingen,Friedrich-Hund-Platz1,37077,G¨ottingen,Germanye-mail:mverdugo@astro.physik.uni-goettingen.de

EuropeanSouthernObservatory,Karl-Schwarzschild-Strasse2,85748,GarchingbeiMuenchen,GermanyArgelander-Institutf¨urAstronomie,Universit¨atBonn

OxfordAstrophysics,DepartmentofPhysics,UniversityofOxford,KebleRoad,Oxford,OX13RH,UK.

ABSTRACT

Context.Inthelocaluniverse,therelativefractionsofgalaxytypesdi ersingalaxyclustersincomparisontothe eld.Observationsathigherredshiftprovideevidencethatclustergalaxiesevolvewithlookbacktime.Thiscouldbedueeithertothelateassemblyofclusters,whichispredictedbybottom-upscenariosofstructureformation,ortocluster-speci cinteractionprocesses.

Aims.Todisentanglevariouse ects,weexploretheevolutionarystatusofgalaxiesfromthecenterofclustersouttotheirinfallregionsinz≈0.25clusters.

Methods.WeconductedapanoramicspectroscopiccampaignwithMOSCAattheCalarAltoobservatory.Weacquiredlow-resolutionspectraofmorethan500objects.Approximately150ofthesespectrawereofgalaxiesthataremembersofsixdi erentclusters,whichdi erinintrinsicX-rayluminosity.Thewavelengthrangeallowsustoquantifythestarformationactivitybyusingthe[Oii]andtheHαemissionlines.Thisactivityisexaminedintermsofthelarge-scaleenvironmentexpressedbytheclustercentricdistanceofthegalaxiesaswellasonlocalscalesgivenbythespatialgalaxydensities.

Results.Thegeneraldeclineinstar-formationactivityobservedforgalaxiesinsidenearbyclustersisalsoseenatz≈0.25.Aglobalsuppressionofstar-formationisdetectedintheoutskirtsofclusters,atabout3Rvirial,wherethegalaxydensitiesarelowandtheintra-clustermediumisveryshallow.Galaxieswithongoingstar-formationhavesimilaractivity,regardlessoftheenvironment.Therefore,thedeclineofthestar-formationactivityinsidetheinvestigatedclustersisdrivenmainlybythesigni cantchangeinthefractionofactiveversuspassivepopulations.Thissuggeststhatthesuppressionofthestar-formationactivityoccursonshorttimescales.Wedetectasigni cantpopulationofredstar-forminggalaxieswhosecolorsareconsistentwiththered-sequenceofpassivegalaxies.Theyappeartobeinanintermediateevolutionarystagebetweenactiveandpassivetypes.

Conclusions.Sinceasuppressionofstar-formationactivityismeasuredatlargeclustercentricdistancesandlowprojecteddensities,purelycluster-speci cphenomenacannotfullyexplaintheobservedtrends.Therefore,assuggestedbyotherstudies,groupprepro-cessingmayplayanimportantroleintransforminggalaxiesbeforetheyenterintotheclusterenvironment.Sincemodelspredictthatasigni cantfractionofgalaxiesobservedintheoutskirtsmayhavealreadytransversedthroughtheclustercenterandintraclustermedia,thee ectsofram-pressurestrippingcannot,however,beneglected;thisis,inaddition,truebecauseram-pressurestrippingmayevenbee ective,undercertainconditions,insidegroupenvironments.

Keywords.galaxies:clusters:general–galaxies:evolution–galaxies:stellarcontent–galaxies:distancesandredshifts

1.Introduction

ThestudyofthegalaxypopulationinsideclustersdatesbacktoHubble(1936),whonotedthatclusterofgalaxiesaredomi-natedbyellipticalandlenticulargalaxies,andthesurrounding eldbyspirals.Severalmodernstudieshavequanti edthisef-fect(e.g.Dressler1980;Gotoetal.2003),whichisnowknownasthemorphology-densityrelation.IthasbeensuggestedthatspiralgalaxiesarebeingtransformedintoS0sbycluster-speci cprocesses.FurtherevidenceisprovidedbyDressleretal.

(1997),

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

2Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

Although,modelspredictthatwhenagalaxyquenchesitsstar-formationitmovesontothered-sequencequiterapidly(～400Myr,Harkeretal.2006).Evidenceofthisisprovidedbythestrongbimodalityobservedingalaxycolors(e.g.Baloghetal.2004b),whichcannotbesimplyexplainedother-wise.

Thequestionabouttheenvironmentaldependenceofgalaxyphysicalpropertiescanbeaddressedbystudiesthatusemorereliableindicators,suchasemissionlines.Thosestud-ies ndstrongcorrelationsbetweenstar-formationactivityandgalaxyenvironment(e.g.Baloghetal.1999;Lewisetal.2002;G´omezetal.2003;Pimbbletetal.2006;Hainesetal.2007).Furthermore,theserelationsdonotappeartodependonthemassofthesysteminwhichthegalaxiesareembedded(Popessoetal.2007).

SincethehierarchicalmassassemblywithtimeisanaturalpredictionofΛCDMcosmologies,itisobvioustolinkthede-clineofthevolume-averagedstar-formationrate(Hopkins2004andreferencestherein)andthegalaxyevolutioningeneraltothegrowthofstructure.However,therelativeimportanceofthedi erentprocessesthatact,isnotyetclear.

Observationssuggestthat,atleast,twodi erentphenomenaarerequired.Oneprocessactsonthestellarpopulationstotermi-natethestar-formationactivityandanotherprocesschangesthegalaxystructure.Ram-pressurestripping(e.g.Quilisetal.2000)isknowntobeverye ectiveinremovingthegalaxycoldgasandthusquenchingthestar-formationactivity,butonlyworksunderspecialconditionspresentinclustercoreswheretheintra-clustergasdensityandtherelativegalaxyvelocitiesarehigh.Thesoftervariantofram-pressurestripping,strangulationorstarvation(e.g.Bekkietal.2002),removesthethingaseoushalopresentaroundgalaxies,andthestar-formationcontinuesuntiltheremainingdiskgasisconsumed.

Otherpossiblemechanismsaregalaxy-galaxymergingandlow-velocitygalaxyinteractionsthattriggeranepisodeofhighstar-formation,whichconsumesahighfractionofgasinashorttimeandmaystripptheremainingviagravitationalshocksandfeedbackprocesses(rson&Tinsley1978;Bekki2001).Thismayprovideexplanationtomodernobservationswherethedecreaseofstarformationactivityhasbeendetectedalreadyatverylowgalaxydensities(Lewisetal.2002;G´omezetal.2003).However,othermechanismsarenecessarytoexplainthechangeinmorphology.Mergersareknowntobee cientinchanginglate-typegalaxiesintoellipticals(Toomreetal.1977;Hernquist1992),buttherelativevelocitiesmustbelow,whichisnotthecaseinclusters.Butthegalaxystructurecanbechangedonlongertimescalesbyharassment(Mooreetal.1998)duetohigh-velocityencountersbetweenclustergalaxies(seealsoGnedin2003).

Despitetheaccumulationofobservationalevidenceovertheyears,thelinkbetweenthegrowthofstructurewithtimeandgalaxyevolutionremainselusiveandthefundamentalquestionsremainunanswered.Howrapidlyandsigni cantlyissupressedthestar-formationactivityininfallinggalaxies?Whatexactlyistheenvironmentaldependenceofthestar-formationactivity?Isitsuppressedmainlyduetolocalorglobalprocesses?Whatisthepredominantmechanism?

Studyingclustersathigherredshiftmayprovidenewcluesabouttheprocessesinvolved,becausetheglobalstar-formationactivitywashigherinthepastandclustersshowatallredshiftmuchloweractivitywhencomparedwiththesurrounding eld(e.g.Baloghetal.1999).Modelsalsopredictthatinthepastthegalaxy-infallingratemusthavebeenhigher(e.g.Bower1991).Theprocessesatworkmustthereforehavebeenincreasingly

moree ectiveatincreasinglyhigherredshift,andathigherred-shifttheprobabilityofobservingtheprocessesinaction,in-creases.

Severalstudiesathigherredshifthavefocusedonthecentralpartsofclusters(e.g.Baloghetal.1999,2002a;Poggiantietal.2006),but,asstudiesatz≈0show,therelationbetweenstar-formationactivityanddensityisalreadydiscernibleatlowgalaxydensities,insidetheinfallingregionswherethegalaxies,whichareinfallingfromthe eld,maybegintoexperiencethein uenceofcluster,andinteractionsbecomemorefrequent.

Eveninthedistantuniverse,clustersofgalaxiesprojectalargesolidangle,andwide- eldobservationsarethereforere-quired.Thecontaminationduetoforegroundandbackgroundobjectsislarger,

Wereporttheresultsofaprojecttostudygalaxyevolutionfromtheinfallingregionstotheclustercenters,coveringpro-jectedradialdistancesoutto4virialradiiforsixclustersat byz Gerken≈0.25.etFirstal.(2004).resultsforInSect.twoclusters2wedescribewerealreadytheobservationspublishedaswellasthemethodusedtomeasuretheimportantparametersofthegalaxies.InSect.3wedescribeclusteridenti cationandothergeneralpropertiesincludingtheenvironmentalde nition.InSect.4wedescribeindetaileachobserved eld.InSect.5weshowthemainresults,discussingtheirimplicationsinSect.6.InSect.7weexploresomepropertiesofthestar-formingpopula-tion.OursummaryandconclusionsareprovidedinSect.8.

Throughout1thispaper,weuseacosmologyofHMpc 1, .3and 0=70kms m=0Λ=0.7.

2.Thedata

2.1.Clusterselection

ThesamplewasselectedfromtheX-rayDarkClusterSurvey(XDCS,Gilbanketal.2004)whoseaimwastocompareX-rayandopticalidenti cationalgorithmsofclusters.Forthispur-pose,deep,opticalimagingofRIXOS elds(Masonetal.2000)wasacquired,whichwereimagedintheX-raybytheROSATPositionSensitiveProportionalCounter(PSPC).SomeoftheX-raydatawerealsoanalyzedbyVikhlininetal.(1998),andlaterbyMullisetal.(2003),fromwhichtheX-ray uxesweretaken.TheXDCSprovidesuswithVandI-bandphotometrytakenwiththeWideFieldCamera(WFC)attheIsaacNewtontele-scope(LaPalma,Spain).Thiscamerahasa eldofview(FOV)of34×34arcmin.

Weselectedforfollow-upspectroscopythree eldscontain-ing,inprojection,twoclusterseach,thusincreasingtheprob-abilityoftargetingaclustermember.TheclustershaveawiderangeofX-rayluminositiesandprobablydi erentevolutionarystates.Theyareatsimilarredshifts,makingthemgoodcandi-datestoprobeevolutionuniquelyduetoenvironmentale ectsatacosmologicalepochwithlook-backtimesof～3.0Gyr.

AsummaryoftheclusterpropertiescanbefoundinTable1.Detailsofhowthedi erentquantitieswerecalculatedarede-scribedintheforthcomingsections.2.2.Observations

Thespectroscopywasperformedwiththemulti-objectspectro-graphMOSCA1mountedatthe3.5meterstelescopeatCalarAltoObservatory(Spain).Theseobservationswerecarriedoutintworuns,from10to15Februaryand20to24March,2002.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters3

Table1.Mainparametersfortheclustersample.TheclusterdenominationscomefromVikhlininetal.(1998)(VMF)andGilbanketal.(2004)(XDCS).CoordinatesaregivenwithrespecttotheX-raycentroid.X-ray uxesaretakenfromMullisetal.(2003).Rvirialisthevirialradiusandσthevelocitydispersion.Nisthenumberofmembersidenti edineachcluster.

FieldClusterAlternativenameRADECz

fX

[10 14ergs/scm2]LX,bol

[1043ergs/s]σ[km/s]Rvirial[Mpc]

N

500,whichencom-

passesawidewavelengthrange,from4300Åto8200Å,allow-ingustostudyboththe[Oii]λ3727andtheHαemissionlines,atthetargetedredshifts,whicharecriticaltostudystar-formationactivityingalaxies.ThegrismprovidesaspectralresolutionofR～10 15Å,whichcorrespondsintherest-frameto8 12Å,forourslitwidthof1arcsec.

Theexposuretimesrangedbetweenoneandthreehoursde-pendingontheapparentmagnitudesoftheobjectsselected.Inafewcasesthesetimeswereincreasedtoaccountforvariationsintheweather.Themagnitudedistributionofthe nalsampleinFig.1.TheselectionofobjectsforspectroscopywasbasedonlyontheirI-bandmagnitudestoavoidanycolorbias.Additionalrestrictionswereimposedbymasksgeometry.

Intotal,537spectrawereacquired.Forouranalysis,wein-cludedinaddition21spectrafromourpreviousprojects“LowX-rayluminosityclusters”(Baloghetal.2002a)intheR265 eldand“X-darkclustersurvey”(Gilbanketal.2004)intheR220 eld.Thiswaspossiblebecausethosespectrawereob-servedusingasimilarinstrumentalsetup.However,wereex-aminedallspectratobeabletoapplythesamecriteriaforthewholesample.Finally,wefoundthat297spectraweresuitableforanalysis(seebelowfortheprecisecriteriaused).2.3.Datareduction

OurdatareductionproceduresweredescribedinGerkenetal.(2004)andcanbesummarizedbythefollowingsteps:Biassub-traction,extractionofindividualslits,correctionofthedistortioninducedbythefocalreducerinMOSCA, at- elding,skysub-traction,extractionoftheone-dimensionalspectra,wavelengthcalibration,andcombinationoftheindividualexposures.

Allofthesetaskswereperformedwithinthemidas2environ-ment,interactively,usingcustom-maderoutines.Eachspectrumwasvisually-inspectedtodetectpecularitiesthatmaya ectthemeasurements.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

4Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25

clusters

Fig.1.Thecombinedselectionfunctionforthewholesample.ThehistogramsshowtheI-bandmagnitudedistributionforthephotometric(dashedredline)andspectroscopic(bluesolidline).Thepointsshowthefractionofgalaxiesforwhichwederivedredshifts.TheerrorbarsarePoissondistributederrors(Gehrels1986).

signi cantdi erenceinthedistributionofstar-formingversuspassivegalaxieswasobserved,withtheexceptionoftwofaintstar-forminggalaxies.2.6.Selectionfunction

Inall elds,onlyafractionofthegalaxiesbelowourspectro-scopiclimit(I≈19.5mag)wasobserved.Therefore,selectione ectsmaybepresentandneedtobecorrected.Thisisachievedbyconstructingaselectionfunction.However,aspartofthe eldswerecoveredbyadi erentnumberofslitmasks(somehadonlyone,otherstwo),andthegalaxydistributionisnotuni-formacrossthe eld,wedevelopedtwoselectionfunctionforeach eldtakenintoconsiderationthesee ects.

Theindividualselectionfunctionswerecalculatedbycount-ingthenumberofobjectswithsuccessfulspectroscopy(i.e.re-liableredshifts)versusthenumberofphotometricallydetectedobjectsuptothespectroscopiclimit(I≈19.5)insidetheareascoveredbythecorrespondingspectroscopicmasks,indi erentmagnitudebins.Nobackgroundcorrectionwasapplied,becauseweonlyneededtoknowtherelativenumberofphotometricallyandspectroscopicallyobservedgalaxiestoevaluatethesuccessofourspectroscopy(seealsoSect.2.4).Theresultingfunctionswereappliedtotheclustergalaxiesintheformofweightstothestatisticalpropertiesoftheclustergalaxies.ThecombinedselectionfunctionisshowninFig.1.However,sometestshaveshownusthattheresultsdependlittleontheweightingappliedandarerobustagainstotherconsiderations.2.7.Equivalentwidthsandstar-forminggalaxies

Weuseequivalentwidths(hereafterEWs)asameasureofthelinestrengthsoftheabsorptionandemissionlines.Wemea-suredEWsautomaticallyusingacustom-maderoutine,whichautomaticallycorrectsforthee ectsofcosmicexpansion.Inthecaseof[Oii]andHα,whichareusedastracersofongoingstarformation,weadoptedthede nitiongivenbyBaloghetal.(1999).Weadopttheconventionthattypicalemissionlines

are

Fig.2.V-bandapparentmagnitudeversuscontinuumsignal-to-noiseratioasmeasuredinSect.2.5.Openreddiamondsaregalaxieswithoutemissionlines,whereas lledbluediamondsaregalaxieswithatleastoneemissionline.

shownwithpositivevalueswhendetected,butalso,thattypicalabsorptionlines(e.g.Hδ)arepositiveinabsorption.

TheHαde nitionused,e ectivelyisolatesthetargetedlinefromtheadjacent[Nii](whichwasalsomeasured).Eachspec-trumwasvisuallyinspectedto ndoutwhetheranylinesfellintotheprominenttelluricbands(A&B),werea ectedbysky-subtractionresidualsorbyartifactsinthespectra.Insomecases,thelineswere aggedandnotusedinsubsequentanalyses.

UsuallytheminimumEWthatcouldbereliablymeasuredwas5Å(seeBaloghetal.2002aforademonstrationbasedonsimilardata),thereforegalaxieswithequivalentwidthsW0>5Å,eitherin[Oii]orHα(orboth),areconsideredstarform-inggalaxies.Wewillshowlaterinthispaper(inSect.7andintheAppendixA)thatthisclassi cationisrobustandphysicallymeaningful.

2.8.Absolutemagnitudes

Weusethesoftwarekcorrect(Blanton&Roweis2007)tocal-culatek-correctionsandthusabsolutemagnitudesforgalaxiesinourspectroscopicsample.ThiscodeisbasedonthelateststellarpopulationmodelsofBruzual&Charlot(2003)andphotoion-izationmodelsofKewleyetal.(2001).Asabyproductofthek-correction,thecodealsoderivesstellarmasses,whichwillbeusedinSect.7.

The eldsR265andR285werealsoimagedbySDSS3(Yorketal.2000),therefore,wecanusetheadvantageofmulti-colorphotometry.Unfortunately,theremaining eld(R220)wasnotobservedbytheSDSSandwehavetousetheavailableVandI-bandmagnitudesprovidedbyGilbanketal.(2004)andtherefore,largeruncertaintiesareexpectedinthecalculations.However,wecantesttheaccuracyofthemagnitudesbycom-paringtheresultsobtainedusingthetwo-bandphotometryandthemulti-bandphotometryintheothertwo elds.Forouranal-ysis,weobtainedB,VandRrest-frameabsolutemagnitudes(intheVegasystemusingJohnson- lterde nitions).

Wefoundscattersof～0.2magando setsof～0.15magbe-tweenthemagnitudesobtainedineitherway.Theo sets

depend

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

5

Fig.3.Redshiftdistributionofthetargetsinthethree elds,withtheclusternamesmarked.The

smallarrowsmarkthepositionofthegroupcandidates(seeSect.4).

onredshiftandcanbecorrectedusingalinear tting.Thescat-terisinagreeswithvaluesfoundbyBlantonetal.(2005)fortransformationsbetweendi erent ltersystems.Thesedi er-encesaresmallandhardlychangetheconclusionsinthisstudy.Weselectedtheoriginalabsolutemagnitudescalculatedus-ingtheSDSSphotometryfortheR265andR285 eldsandap-pliedtheredshiftcorrectionforthegalaxiesinR220toonlythemagnitudesderivedusingtheVandI-bandphotometry.Allap-parentmagnitudeswerecorrectedforGalacticextinctionusingthemapsofSchlegeletal.(1998).Nocorrectionforinternalab-sorptionwasattempted,sincewedonothaveinformation,inmanycases,aboutgalaxyinclination,andtheBalmerdecrementcannotbeusedinallcasesbecauseHβisrarelydetectedforemissionlinesgalaxies,anduncertaintiesforpassivegalaxieswillremain.Noimportantdi erenceswerefoundbetweentheabsolutemagnitudedistributionsforthe eldandclustersam-ple.

ThestellarmassesweretestedagainsttheformulaeofBelletal.(2005)usingourrestframeBandV-bandmagnitudes.Wefounddeviationsonlyatthehighmassend.Sincethekcor-rectcodeisreliableinpredictingmagnitudesbetweentheSDSSandoursystem,wepreferredtouseitsdataoutputs.

3.Theclusters

3.1.Clustermembership

Ineach eld,theredshiftdistributionwasanalyzedtodetectprominentstructures.Theclustersstudiedhadalreadyknownredshifts,withtheexceptionofthoseintheR220 eldwhoseredshiftswereunclear(seeSect.4fordetails),butwerecon- rmed.Themeanclusterredshift(z)andvelocitydispersion(σ)werecalculatedusingthebi-weightestimatorsofBeersetal.(1990)anditerativelyexcludinggalaxiesbeyond3-σofthemeanredshiftuntilthesolutionconverged.Weappliedaboot-

Fig.4.Color-magnitudediagramsofthemembersofthesixob-servedclusters.Filledbluediamondsarestar-forminggalaxies,whereasopenreddiamondsarepassivegalaxies.Theshadedar-easarede nedbythe3-σdeviationoftheleastsquares tstothepassivegalaxies.TheverticaldashedlinemarkMusedinthedensitycalculation(seeSect.3.5).WenoteI≈the 21red.4star-forminggalaxiesbelongingtothered-sequenceandevenredderinsomeoftheclusters.

strappingtechniquetocheckthestabilityoftheresultsandcal-culatetheerrorsinthevelocitydispersion.TheresultscanbefoundinTable1andtheredshiftdistributioninFig.3.3.2.Galaxycolors

Weusethespectroscopicinformationtoseparatethegalaxypopulation.Galaxieswithemissionlinesareconsideredstar-formingandthosewithoutemission,passive(seeSect.2.7).PlottingtheV IcolorversusI-bandmagnitude(Fig.4)forclustergalaxiesshowsthatallclustershaveclearred-sequences.Onlyfewclustergalaxieshavebluecolorsbutnoemissionlines.

Thedistributionofthepassivegalaxies,thered-sequence,iswelldescribedbysimpleleast-squares ts.Theweightedmeandispersionofthered-sequencesisσ≈0.05mag,whichisthetypicalerrorinthephotometry.Allgalaxiesredderthanthelower3-σlimitareconsideredredgalaxies,andblueotherwise.Giventhiscriterion,wenotetheexistenceofapopulationofredstar-forminggalaxiesbelongingtothered-sequenceandevenredder.Morestrikingisthehighnumberofthosegalaxiesbe-longingtotheclusterVMF74.Someofthecharacteristicsofthissub-populationwillbedescribedinSect.7.3.3.X-rayluminosities

TheX-rayluminositiesoftheintraclustermediumandclustervelocitydispersionsareindicatorsofclustermasses.Thecorre-lationbetweenthesetwoparametershasbeenextensivelystud-ied(e.g.Markevitch1998;Davidetal.1993;Xue&Wu2000)andisinterpretedasasignofdynamicalequilibrium,even

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

6Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25

clusters

Fig.5.

BolometricX-rayluminosityplottedagainstvelocitydis-persion.Opencircles(Markevitch1998),crosses(Davidetal.1993)andstars(Xue&Wu2000)representtheLforlocalclusters.ThesixclustersstudiedhereareplottedX-σrelationasdi-amondswitherrorbarsinthevelocitydispersion.

thoughthelargescatterinthelocalrelationindicatesdeviationfromthisequilibrium.Nevertheless,laterstudieshavefoundthatclustermassesderivedfromusingindependentmethods,includ-inggravitationalweak-lensing,correlatewithrelativesmallscat-ter(e.g.Hicksetal.2006),solvingalong-standingcontroversy.InFig.5,weplotthebolometricX-rayluminositiesagainstthederivedvelocitydispersions.TheclustersfollowthelocalLisXunderluminous σrelation,withfortheitsnotablevelocityexceptiondispersion.ofXDCS220,Thisclusterwhichdis-playsatailintheredshiftspace,whichcomplicatesthecalcu-lationofthevelocitydispersionandimplies,therefore,thatitislikelyoverestimated.

Inaddition,VMF194ispeculiar,becauseithasavelocitydispersionthatistoolowforitsX-rayluminosity.Thise ectmaycomefromtwodi erentsources.First,σmaybeunderesti-matedduetoselectione ectsgiventhelownumberofmembersidenti ed.Second,wedetectabackgroundgroupatz≈0.24ofarelativelargevelocitydispersion(seeSect.4.1),whichmayhavecontaminatedtheX-raymeasurements.Nevertheless,thisclusterdoesnotappeartobesoextremelyo setfromtheLrelationasXDCS220.

X σWiththeexceptionofXDCS220,theclusterX-rayluminosi-tiesandvelocitydispersionsaresimilartothoseofVirgo,A496andComaclusters(e.g.Davidetal.1993;Rinesetal.2003)andthusareexpectedtobeclustersthatareasequallymassive.3.4.Virialradius

Fromtheresultsshownintheprevioussection,itispossibletoassumethattheclusterssampledinthisstudyareingen-eralindynamicalequilibrium4andtherefore,thevirialtheoremisapplicable.Theradiuswithinwhichthevirialmassisesti-matedtobecontainediscalledthevirialradius.Accordingtotheobservationally-calibratedderivationsofCarlbergetal.(1997),Rvirialisde nedasthedistancewherethemeaninnerclusterdensityis200timesthecriticaldensity

4

ItisprobablynottrueforXDCS220,howeverforthesakeofcom-parisonitwillbeassumedthatitis.VMF194isalsopeculiar,butthedi erencesmayarisefromanothersources.

Fig.6.Relationbetweenvirialradiusandprojecteddensitybe-foreandaftercorrectionfor eldcontamination.Theopenredcirclesarepassivegalaxies,whereas lledbluecirclesarestar-forminggalaxies.

itisalsocalledr200.Itsrelationtothevelocitydispersionσisgivenby

Rr√

σ

virial=200=

10 1 m(1+z)3+ =0.7andλforaHubbleconstantof

H0=70kmsMpc 1, λ Rm=0.3.

Sincer200(virial)characterizesthesizeofclustersfollow-ingtheassumptionofauniversalmasspro le,itisusefulasanenvironmentalindicatorofmassdensity,giventheclustercentricdistancesofclustergalaxies.Thereforethedistancesofgalax-iestothecenteroftheclusterarenormalizedbytherespectiveclustervirialradius,allowingtheentiresampletobecombinedintoasinglecluster,increasingthestatisticalsigni canceofouranalysisandreducingthee ectsofcluster-to-clustervariations.3.5.Projecteddensity

Anothercommonindicatorofenvironmentisthelocalnum-berprojected(2-D)densityofgalaxies.Itscalculationdoesnotmakeanyassumptionaboutthephysicalpropertiesoftheclus-ters,butotherprecautionsmustbetaken.First,thegalaxynum-berdensityisafunctionofluminosity.ThespectroscopiclimitofI≈19.5magcorrespondstoMmostcluster(z≈0.3)andMI≈ 21.4forthefurther-(z≈0.2),takinginconsiderationI≈the typical20.2fork-correctionstheclosest(seeoneFukugitaetal.1995).

Foreachcluster,thephotometriccatalogwasdividedusinganapparentmagnitudethatcorrespondsonaverage,tothelumi-nositylimitofthemostdistantcluster,whichtranslatesintoanapparentmagnitudecutofI≈18.3atz=0.18(seeFig.4).

Theprojecteddensityisde nedbytheareathatencirclesthe fthnearestneighbortothisgalaxy,whichisreferredasΣ5.However,signi cantforegroundandbackgroundcontami-nationisexpectedandmustbecorrectedbeforecompletinganystatisticalanalyses.Intheliterature,severalmethodsofdi er-entcomplexityaredescribedtodealwiththisproblem.Mostofthemsubtractavalue(localorglobal)fromthecalculateddensity,makingdi erentassumptions.However,thosemethodsoftenyieldunphysicalvalues(i.e.negativenumbers)fortheden-sityestimates.Ourcaseisevenmorecomplicated,becausewedonotonlyhave eldcontamination,butalsocontaminationfromtheotherprojectedcluster.Therefore,wechoseanotherap-proachusingincombinationthephotometricandspectroscopicdata-set.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

7

Fig.7.Representationofthe eldsoftheobservedclustersasindicatedbythenamesontheindividual gures.Onlyclustermembersareshown.Blue lledandopenredsymbolsrepresentstar-formingandpassivegalaxiesrespectively.Theclustercentersaremarkedwithlargeverticalcrossesandthelargeconcentriccirclesrepresentoneandtwovirialradiirespectively.Thecontoursarethedensitymapsofallgalaxieswithcolorscompatiblewiththered-sequenceoftherespectivecluster(seeSect.4).ThearrowsintheVMF194plotindicatethepositionofarichbackgroundgroup(seeSect.4.1).IfthetruenumberdensityofgalaxiesinacertainregionoftheclusterisN(unknown)andtheobservedisM(determinedfromthephotometriccatalogandincludingthecontamination),onehasarelativefractionoff=N/M.Fromthespectroscopicdataset,weknowthattherearengalaxiesbelongingtotheclus-terandmisthenumberoftotalobservedgalaxiesinthesameareawithsecureredshifts.Sincetheselectionwasperformedrandomly(basedonlyonI-bandmagnitudes),wecanassumethatwehavethesamefractionexpressednowbyf=n/m,thus

wecancorrecttheobservedvalueM,multiplyingitbyn/m,ob-tainingN.

Theareasusedtomakethesecorrectionsarelargerthantheareasconsideredbytheindividualdensitycalculations.Theyen-circlealways10galaxieswithsecureredshifts,andwecountthenumberofclustermembersversusthenon-clustergalaxies.Havingahigh- llingfactorhelpstothestatisticalreliabilityofthissimplemethod,becausetheareassampledwillhavesmallerphysicalsizesandthussmallerdeviationsfromthelocaldensity.TheresultsofthecorrectioncanbeseeninFig.6.Afterthispro-

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

8Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25

clusters

Fig.7.continued.Representationoftheobservedclustersasindicatedbythenamesontheindividual gures.Onlyclustermembersareshown.Blue lledsymbolsarestar-forminggalaxiesandopenredarepassiveones.ThearrowsinVMF73showthepositionoftheX-raystructuredetectedbyRasmussen&Ponman(2004)(seeSect.4.3).cess,acorrelationbetweenvirialradiusandprojecteddensitybecomesevident.

Wewouldliketoemphasizethatthedensitiescalculatedherearenotdirectlycomparabletothosecalculatedelsewhere,be-causethemagnitudecutsandapproachestosubtracttheback-groundvarybetweendi erentauthors.

Finally,galaxiesfainterthantheindividualclustermagni-tudecutwerenotincludedinthecompositecluster;thisreducedthe nalsamplesizeto～120galaxies.Wenotethat,manyofthegalaxiesexcludedarememberoftheVMF74cluster.

ti edmembersareactuallyassociatedwithstructuresthatshowupusingthissimplecolorcut.4.1.R220

4.Descriptionofthe elds

Wedescribeeach eld,providingdetailinparticularofthegen-eralclusterproperties,candidategroups,andclustersubstruc-ture.EachclusterisrepresentedseparatelyinFig.7,withdif-ferentsymbolsforstar-formingandpassivegalaxies.ThelargeconcentriccirclesrepresentoneandtwovirialradiirespectivelycalculatedaccordingtoEq.1.

ThecontoursshowthedistributionofallgalaxiesdowntoI=23magwithcolorssimilartotherespectivered-sequences(seeFig.4).Theyprovidesomeinformationaboutthespatialdistributionofgalaxieswithoutspectroscopy.SincetheCMRforellipticalshaslittlescatter,thestructuresareprobablyatsimilarredshifts.Thistechniquehasbeensuccessfullyusedbyotherstudiestodetectsubstructuresaroundclusters(e.g.Kodamaetal.2001;Tanakaetal.2005).Inthiscase,however,itisnotpossibleto rmlystatethesigni canceofthosestructuresbecauseonlytheV Icolor,providedbyGilbanketal.(2004),isusedandthered-sequencesofeachprojectedclusterhavesimilarcolors(seeFig.4).TheuseoftheSDSSmulti-colorphotome-trydoesnothelpbecausetheiruncertaintiesarelargeratfaintluminositiesandthered-sequencesbecomecompletelyblended.Therefore,thecontoursplottedineach guremustbetakenonlyasinformative.Nonetheless,manyofthespectroscopicallyiden-

TheR220 eldisaverycomplex eld.Thereis, rst,alargernumberofobjectsthanintheother elds.Thisismaybeduetoitslowergalacticlatitude.Ourphotometriccatalogwascleanedofstar-likeobjects,but,theseparationisnotperfectandmanyofourslitsunintentionallycontainedstars,losingtheadvantageofhavinganextramaskforthis eld(8insteadof7).Theredshiftdistributionalsolooksmorecomplex(seeFig.3),withanumberofassociationsbesidesthetwoclusters.

TheclusterVMF194wasfoundtobedi culttocon rmop-ticallybyVikhlininetal.(1998)andcollaborators.AccordingtoGilbanketal.(2004),theproposedclustercorrespondsto“averyextendedX-rayemissionandthegalaxyover-densityissimilarlyextended”.Here,VMF194at z =0.210(seeTable1)wasunequivocallydetected,butthedataobtainedshowedthattheclusterhasasurprisinglylowvelocitydispersionforitsX-rayluminosity(seeFig.5).Threeadditionalgalaxieshaveredshiftsthatimplyclustermembership,accordingtothepreviously-measured3-sigmalimits;thesegalaxiesarelocated,however,atlargeclustercentricradii(>7Rvirial).Whentheyareincluded,thevelocitydispersiondoesnotchangesubstantially,andthustheywereexcludedasmembers,butnotincludedinthe eldsample.

Atanangulardistanceof～4.4arcminofVMF194(i.e.al-mostoverlappingpositions),wedetectaclumpofgalaxiesatredshift z =0.243.Thisclumpalsoshowsupinthespatialdis-tribution:8outofthe11galaxiesareclusteredinanareasmallerthan～0.3×0.7Mpc.Thevelocitydispersionofthisgroupisσ=401±74km/s,indicatingthatitmaybequitemassive.Nored-sequenceisdetectedand4outofthe8galaxies,showstar-formingactivity.Thisgroupmayhavebeenthecauseofconfu-

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters9

Table2.Mainparametersforthegroupscandidatesforour elds.Theiridenti cationcodesshowtheaveragepositionsofthemembers.Meanredshifts(z)andaveragedeviationsareshownasvelocities(σ).Thebiweightestimatorswereusedonlyingroupswithatleast8members.Thegroupnumberidentifymembergalaxiesintheonlinetable.

GroupID

z σN[kms 1]1J172604+742830

0.053

126

4

2r220

3J172958+7442040.243

401

8(11)

4

r265

sioninallpreviousstudiesinthis eld.Infact,theconcentrationofgalaxiesismoreprominentfor

thisgroupthanforVMF194whenselectedbyacolorcut(seeFig.7).

Wecon rmthepresenceoftheclusterat z =0.261detectedbyGilbanketal.(2004),whichistherereferredasXDCScmJ172333+744410(itiscalledhereXDCS220forshort).Wecon rmtheredshiftcalculatedthere.ThisclusterhasaverylowX-rayluminosityandpassedundetectedintheX-rayanalysisofVikhlininetal.(1998)andMullisetal.(2003).Itdisplaysalargevelocitydispersion(seeTable1),whichisprob-ablyoverestimatedbecauseoftheexistenceofatailinredshiftspace.Excludingmembersthatarelocatedatlargeclustercentricdistancesdoesnotchangethebiweightestimateofthevelocitydispersion.Weconcludethatitisarealfeatureofthecluster,whichisprobablyintheprocessofrelaxingorhasanextendedstructurealongthelineofsight.Thisclustershowsaclearred-sequenceand5out14galaxiesshowongoingstar-formingac-tivity.

Twoothergroupcandidateswerefound(seeTable2),oneat z. 3×=00.7.04293Mpc),(all±390beingkmstar-forming/s)with6membersgalaxies,inand1Mpc2(or5in0theotherisat z =0.05274(±126km/s),withfourmembersin0.3×0.4Mpc.4.2.R265

ThecentralpartsoftheclusterVMF131werepreviouslyob-servedbyBaloghetal.(2002a)aspartoftheirlowluminosityX-rayclusterproject,whereitwasknownasCL1309+32,usingthesameinstrumentandsetup;wehavethereforeaddedtheirdataintoourstudy.Since,itisthemostdistantclusterstudied,wewereabletodetectmembersuptoclustercentricdistancesofR>4Rclustervirial.ThecolorcontoursshowslittlesubstructurearoundthebutthecentraloverdensityisclearlyvisibleinFig.7.TheclusterVMF132istherichestclusterinoursampleandhasthelargestvelocitydispersionandthusthelargestvirialra-dius,occupyingalargeproportionofthe eld.Inspiteofthis,thegalaxyconcentrationisclearlyirregularwhencolorcutsareappliedandonlysparsestructuresaredetected.

Anextendedgroupwasalsodetectedat z =0.186±0.001185(349km/s)with8membersinanareaof1×2Mpc,or0.7×1.5Mpcifoneexcludesonegalaxy.4.3.R285

Thetwoclusterspresentinthis eldalmostoverlapintheirpo-sitionsonthesky(angularseparation～5arcmin,seeFig.7).Inaddition,weplacedmoremasksinthecentralpartsoftheclus-ters,whichledtoahighersuccessratecomparedwiththeother elds.TheclusterVMF73atz=0.254hasthelargestnumber

Fig.8.Fractionofblueclustergalaxies(asde nedinSect.5.1)againstnormalizedvirialradiusandprojecteddensity.ofmembersidenti ed(N=44).Mostoftheidenti edmembersofthisclusterarelocatedinside1RturerunningapproximatelyintheEast-Westvirial,inanelongatedstruc-direction.Infact,whengalaxiesareselectedbythecolorsofthered-sequencethisstructureisclearlyvisible.Unfortunately,theforegroundclus-ter(VMF74)hasaCMRwithverysimilarcolors(seeFig.4)anditisnotpossibletoseparateclearlybothclustersusingthistechnique.

Theclustercenterisapproximatelyatthemiddleofthisstructure,butinoneextreme,2atadistance～1Rvirial,acompactgroup(100×100kpc)ofbright,passivegalaxiesisfound.TheirpositionscoincidewiththeextendedX-raysourceXMMJ0943.9+1641detectedbyRasmussen&Ponman(2004).TheX-ray uxofthisstructureisfprivatecommunication),X,1 2keV=3×10 14ergcm 2s 1(Rasmussen,whichyieldsanX-rayluminosityLX,bol=1.38×1043ergswiththeVMF73 1,assumingthattheX-raystructureisassociatedcluster.Thisstructuremaybethecenterofalarge,newlyinfallinggroupofgalaxies,althoughnopeculiaritiesweredetectedintheredshiftdistribu-tion.

TheclusterVMF74hasasurprisinglylargenumberofstar-formingmembers:19outof34,andmanyofthemhavecolorssimilartotheredsequence(seeFig.4).Itisalsotheclosestoftheclustersstudiedwithameanredshiftofz=0.18.Thespectroscopically-identi edmembersarealsodistributedinaelongatedstructureinanalmostNorth-Southdirection,althoughlessclearthaninVMF73.Italsoshowsupusingcolorcuts.Theclustercenterliesatthenorthernextremeofthisstructure.

AccordingtotheXMM–NewtonX-rayanalysisofRasmussen&Ponman(2004),bothVMFclustersdonotexhibitpeculiaritiesandarefairlytypicalfortheirmasses.4.4.Fieldsample

The eldsampleconsistofallgalaxiesbetween0.15<z<0.35,withatleast6-σofdistanceintheredshiftspacefromtheclusters.Weincludedthegalaxiesbelongingtothesuspectedgroups.Sincethesampleisbuiltusingthesameobservationsanycomparisonisstraightforward.Thesameredshift-dependentmagnitudecutshavebeenapplied,whichyields97galaxiesusedfordirectcomparison.Throughoutthispaper,manyquantitieswillbecomparedwiththoseofthissubset.

5.Analysisofthecompositecluster

5.1.Galaxycolorsandenvironment

InFig.8,weplotthefractionofbluegalaxies(asde nedinSect.3.2)againstourenvironmentindicators.Weobserveanin-creaseinthefractioninbothcasestowardslargeradiusandlow

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

10Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

densityregions,howeveranotablepeakinsideR<1RInthehigh-densityregions,thefractionremainsvirialisobserved.lowandisstatisticallysimilarforclustersatthoseredshifts(e.g.Ellingsonetal.2001).

Theshapesofthosetrendsaresimilartothefractioncalcu-latedusingemissionlinesasindicatorsofstar-formationactivity(Fig.9),whichshouldnotbesurprisingsincebluercolorsoftenre ectthepresenceofyoungstellarpopulations.However,thereisanimportantfractionofstar-forminggalaxieswithredcol-ors,andinprincipleitmaybreakdownthepreviousrelation.Theyonlyappeartoa ectthefractionvalue,i.e.thebluefrac-tionislowerthanthestar-formingfractionat xedclustercentricdistancesanddensities,butnottheshapeofthetrends.Wein-vestigatethisfurtherinforthcomingsections.

ThefractionofbluegalaxieswascalculatedoverthenearestNgalaxiestoeachpointintheplane,i.e.insideamovingboxcontaininga xednumberofobjects,centeredoneachgalaxy.MakingthenumberNtoosmallincreasesthenoise;makingittoolargeshortensthedynamicalrangecovered,becausethismethodtruncatestheextremitiesofthelists.Itwasfoundthatusingthenearest15–25pointsisagoodcompromisebetweenspatialcoverageandstability.

Tocheckthestatisticalsigni cance,abootstraptechniquewith2000iterationswasappliedtoeachvalue,takingthemeanandthestandarddeviationofthebootstrappedvalues(checkingpreviouslyifthedistributionsarecompatiblewithGaussian)asthe nalvaluesandtheirerrors,respectively.

Noisecanincreaseordecreaseasoneincludesmoreorfewerpointsinthecalculations,buttheoverallshapesofthecurvesdonotchange,asforthecaseofchoosingarbitrarybins.Thisisparticularlyimportantinsmallsamplesandeventuallyunderthee ectsofsubstructure.Thebootstrappingmethodhelpstochar-acterizethecon denceregion.ThisprocedureisappliedinallsimilarstatisticalanalysesinthisworkAsa nalvisualproce-dure,thelinesweresmoothedwithsimplespline ts;however,thisprocedure,however,onlyeraseslocalscalevariations.5.2.Starformationactivityandenvironment

Weinvestigatefurtherthedependenceofthestar-formationac-tivityonenvironmentbasedonemissionlines,whicharesensi-tivetotheionizingradiationcomingfromthenewly-formedhotstars.Weplottheweightedfractionofstar-forminggalaxies(asde nedinSect.2.7)andthemeanof[Oii]andHαEWsinFig.9,againstnormalizedclustercentricdistanceandprojecteddensity,respectively.The eldvalueisshownasahorizontalareaintheplots.

Weobservethatthestar-formationactivityisstronglysup-pressedintheclustercoreswithlessthan20%ofthegalax-iesformingstars.Thisfractionincreasessteadilyupto～50%atR≈3Rvirial,butitdoesnotreachclearlythe eldvalueof～for56%.thoseofredshiftsstar-forming(seeHammergalaxies.etThisal.1997; eldBaloghfractionetisal.typical1999;Nakataetal.2005).Althougheachoftheseauthorsuseddi er-entcutstode nethestar-formingpopulation,thederivedvaluesagreewithinthestatisticaluncertainties.

However,theincreaseinthestar-formationactivitywithra-diusisirregular.Inasimilarwaytothefractionofbluegalaxies,weobserveapeakatR～0.6Routsidevirialinboth,star-formingfractionandmeanEWs.Onlyof1Rtoincreaseagain.Theexplanationforvirial,thoseindicatorsstartthispeakisdiscussedinSect.6.2.

Themeanfractionofstar-forminggalaxiesincreaseslin-earlytowardslow-densityregionsandreachesthe eldvalue

onlywithintheuncertainties.ThemeanEWsof[Oii]andHαfollowsimilartrends,buttheyalsodisplayapeakatΣgalaxiesMpc 2.ThemeanEWsofthoselinesdisplay5similar～60values,whichareslightlylowerfor[Oii],eventhoughthatinthelocaluniversethetypicalrelationisW0([Oii])≈0.4W0(Hα)(Kennicutt1992).

Theprevioustrendsindicatethatthequenchingofthestar-formingactivitystartsatslightlylargerclustercentricdistancesandlowerprojecteddensitythatthosesampledhere.

Severalstudiesinthelocaluniversehavefoundthatthestar-formationactivityreachesthe eldvalueapproximatelyatclustercentricdistances～2R.(e.g.Lewisvirialandprojecteddensitiesaround～1galaxyMpc 2etal.2002;G´omezetal.2003;Rinesetal.2005).Thoseresultsarecompatiblewiththeresultsfoundhere,althoughthoselowdensitiesarenotreachedinthisstudy,buttheclustercentricdistancesare,andwestillobserveslightstar-formationdepletionatdistancesR>2Rstar-formingfractioninthelocaluniverseisvirial.Asthe eldmuchlower(～35%,seee.g.Rinesetal.2005),theradialtrendfoundinthisstudyis,therefore,steeper,indicatingthatthesuppressionofthestar-formationactivityinclustersatz～0.25wasmoree ec-tive,becausethestar-formingfractionintheinternalregionsofclustersissimilaratallredshifts(e.g.Baloghetal.1999;Nakataetal.2005).

Pimbbletetal.(2006)studiedasampleof11clustersbe-tween0.07<z<0.16,withquitegoodcoverageoutsideof1Rresultspointtowardssimilarconclusionsasvirial.Alhough,thethestudiesatz～0,thebreakinthestar-formationactivityappeartobeshiftedslightlytowardshigherdensities,ane ectthatwecannotcon rmnorexclude,althoughinourcasethefractionap-proachestothe eldvalueatΣdensitycalculation5≈10hampergalaxiesdirectMpccomparisons.

1,butthedif-ferencesontheAthigherredshifts,moststudieshavebeenfocusedonthecentralregionsofclusters(e.g.Baloghetal.1999,2002a,b).Ourresultscomplementthosestudies,samplingsimilarclustersatlargerclustercentricdistances,withfocusonthecluster- eldinterface.Italsobridgesthestudiesbeingperformedbydeepsurveyswhichhavefocusedmainlyonlow-densityregions(e.g.Elbazetal.2007;Cooperetal.2007;Franzettietal.2007).

6.Originofthetrends

Toexploretheoriginoftrendsdescribedintheprevioussection,wesplitthesampleintodi erentsubsamplesaccordingtovari-ouscriteria.

6.1.Thestar-formingpopulation

Weanalyze rstthepropertiesofthestar-formingpopulationonly,de nedtobethegalaxieswithequivalentwidthsWdynamicalrangeofradiusandgalaxydensitiesis0>5Å.Thesmallerbecausethesubsampleissmallerthantheoriginalsample.

ThemeanEWs(Fig.10)remainstableoverawiderangeofclustercentricdistancesanddensityvaluesandarestatisticallysimilartothosefoundfor eldstar-forminggalaxies,whichim-plythatthepopulationsdonotdi ersubstantially.ThisleadstotheconclusionthatthetrendsseeninFig.9aredrivenonlybythechangeintherelativenumbersofstar-formingandpassivegalaxiesindi erentenvironments.

Thisresultissimilartothe ndingsofBaloghetal.(2004a)andRinesetal.(2005)atz≈0whofoundthatthemeanHαEWsdisplayasimilardistributionforstar-forminggalaxieslo-catedin“high”and“low”densityenvironments.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

11

Fig.9.Fractionofstar-forminggalaxies(leftpanels)andmeanEWsof[Oii](middlepanels)andHα(rightpanels)againstnormal-izedclustercentricdistances(toppanels)andprojecteddensitiestothe5thneighbor(Σ5,bottompanels),plottedasthethick,solid,blacklines.Theshadedareasaroundthecurveinlightbluearethestandarddeviationsofthebootstrappedvalues.Thehorizontalareasshowthe eldvaluesforgalaxiesbetween0.15<z<0.

35.

6.2.Subsamplesaccordingtomembership

Giventherelativesmallsampleandsomeunusualfeaturesinthecompositecluster,weinvestigatethein uenceofindivid-ualclustersonthe nalmeasurementsforthecompositecluster.Sincetwoclusters,VMF73andVMF131,accountforanim-portantfractionofthedatausedinthecompositecluster,weinvestigatethemindividually.Here,giventhesmallernumberofgalaxies,weareforcedtousefewerdatapointsinourstatisticalanalyses,whichincreasesthelevelofnoise.

TheresultscanbeseeninFig.11.Wenotestrikingdi er-encesbetweentheclusters,especiallyintheradialdistribution.ThetrendsfortheclusterVMF73showpeaksinside1Rvirial.Therefore,weconcludethatthepeaksdetectedintheglobaltrendsareexclusivelyduetothiscluster.Theexistenceofthispeak,orratherthedepletionat～1Rvirialislikelyane ectofasecondarystructureinthiscluster(seeSect.4.3),becausetheradialgradientisthecombinationofbothsubstructures.ThiscanbetakenasadditionalevidencethattheX-raystructuredetectedbyRasmussen&Ponman(2004)actuallybelongstothecluster.Itmayformpartofaninfallinggroupandclearlyhasanoticeablee ectonthegalaxypopulationofthiscluster.Additionale ectsmayarisefromthegeometricalcon gurationoftheclusteratR<1Rvirial,givenitselongatedgalaxyconcen-tration.ThosefeaturespassedunnoticedinthepreviousanalysisofGerkenetal.(2004)asthe xedbinsusedtheree ectivelyerasedthedetail.

VMF131shows,ontheotherhand,amodestbutsteadyin-creaseinitsstar-formingactivitytowardslargerclustercentricdistances.Thisclusterisquitewellstudiedatlargeradii.Thus,thegeneraltrendsofthecompositeclusteratthesedistancesareverydependentonit.

Fig.10.Similarto gure9butnowanalyzingthedistributionofthestar-formingpopulationonly(i.e.W0([Oii],Hα)>5Å).

Thisbehavioroftheactivegalaxypopulation,togetherwiththestrongbimodality,observedincolors(Baloghetal.2004b)andEWs(Hainesetal.2007),detectedinlargelocalsurveysfa-vorsmechanismsthattriggerarapidevolutionbetweengalaxysubtypes.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

12Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25

clusters

Fig.11.Fractionofstar-forminggalaxiesandmeanequivalentswidthsagainstnormalizedclusterdistanceandprojecteddensityfortheclustersVMF73andVMF131asdepictedintherespectivepanels.Inthebottompanels,dashedbluelinesarefor W0([Oii]) andsolidredlinesfor W0(Hα) bottompanelsthedashedbluelinerepresentthemean[Oii]EWsandthesolidredlinetheHαones.Therespective1-σaremarkedasthehashedareasinthebottompanelsandthindottedlinesintoppanels.Sincedensityprobesenvironmentindependentlyoftheclus-tergeometry,clustersubstructuredoesnota ect,inprinciple,thecorrelations.Nevertheless,weobservethatthetrendsforthesetwoclustersarequitedi erent.VMF73showsasharpin-creaseinthefractionofstar-forminggalaxiestowardslowerpro-jecteddensitiesbutamodestincreaseintheiroverallactivity,asmeasuredbytheirEWs.VMF131displaysanincreaseinitsfractionofstar-formingmembersandtheaveragestar-formationactivityissimilarlyincreased.

Thescatterofthegalaxypopulationinsideclustershasbeenalreadynoted,itdoesnothoweverdependstronglyontheirX-rayluminositynorvelocitydispersionaccordingtoPopessoetal.(2007),althoughPoggiantietal.(2006) ndbothaweakcorrelationofgalaxypropertieswithclustermassandevolutionofthecorrelationwithredshift.Thisscattermayberelatedtomoresubtleproperties,suchasclustersubstructure,mass-assemblyhistoryandintra-clustergasdistribution,aswellasthepropertiesofthelarge-scalestructuresurroundingtheclusters.

stituteonaverage25%oftheentireclusterpopulation.Theysug-gestthatthoseobjectsareintheprocessofevolutionfromlatetoearlytypes.Wolfetal.(2005)identi edhundredsinthe eldofthesuperclusterA901/902(z≈0.17)basedontheinforma-tioncontentinthemedium-bandphotometryoftheCOMBO-17survey.Theyinterpretethecolorofthosegalaxiesasaproductofthecombinationofoldstellarpopulationsanddustextinction.Similarly,Tanakaetal.(2007)presentedindicationofredgalax-ieswithyoungerstellarpopulationsingroupsaroundaz=0.55cluster.Theyarguedthatthoseredgalaxieshavetruncatedtheirstarformationactivityrecently,onashorttimescale,butthattheyhostalargefractionofoldstarsinaadditiontoareason-ableamountofdust.

Ontheotherhand,Martinietal.(2002),basedonROSATX-raydata,reportedanunexpectedlyhighfractionofAGNsinellipticalgalaxiesinamassivez=0.15cluster,whichdidnotshowopticalsignatures.Althoughtheirsampleissmall,thefrac-tionofobscuredAGNsissimilartothefractionofbluegalaxiesidenti edinthatcluster.Furthermore,Yanetal.(2006)foundthatmorethanthehalfofredgalaxiesintheSDSS-DR4showemissionlines,mostofthemconsistentwithbeinglowion-izationnuclearemission-lineregions(LINERs).However,theLINERsmaynotbedueonlytoAGNs,forexampleSarzietal.(2006)reportextendedLINER-likeemissioninseveralearly-typegalaxiesintheirspatially-resolvedspectroscopy.Thereforethequestionisnotclearlysettled.

TodecidewhetherthosegalaxiesareAGNsornot,andtowhatdegreeourstar-forminggalaxiesmaybecontaminatedbynuclearactivity,weperformedsometestsbasedontheemissionlines.WenotethatwemaybeunabletodetectobscuredAGNs.NogalaxyshowssignsofbroadeningtypicalofSeyferts1,butSeyferts2andLINERsmaystillbepresent.Wecalculatetheratiosbetweenemissionlines([Oii],Hβ,[Oiii]λ5007,Hαand[Nii]),whereispossiblesincealllinesarerarelypresentalto-gether.Weconductseparateteststocheckallpossibilities.

The rstclassicaltestputthegalaxiesintotheBPTplane(i.e.log([Oiii]/Hβ)vslog([Nii]/Hα),Baldwinetal.1981).EachparoflinesarecloseenoughtousetheEWsinsteadofthe uxes.

7.Thecaseoftheredstar-forminggalaxies

WealreadynotedinSect.3.2theexistenceofasub-populationofclustergalaxieswithemissionlinesbutredcolors.Twenty- veoutof56star-forminggalaxiesbelongtothispopula-tion.TheiraverageEWsare W0([Oii]) =14.8±2.48Åand W0(Hα) =19.9±4.90Å,respectively,similar(within1-σsig-ni cancelevels)tothemeanstar-formingpopulation(seeFig.10).Theydonotseemtopopulateanyspecialenvironmentinthecluster,beingmoreorlessevenlydistributedinradiusanddensity,whichexplainsthesimilaritybetweentheblueandthestar-formingfraction(Fig.8and9).Theyalsospanthefullrangeofluminositiescoveredbythisstudy.

GalaxieswitharedSEDandstar-formationactivityhavebeenroutinelyreportedatintermediateredshifts,eitherinthe eld(e.g.Hammeretal.1997)orinclusters(e.g.Demarcoetal.2005).InthecaseofthelocalUniverse,arecentpaperbyPopessoetal.(2007)reportsthatredstar-forminggalaxiescon-

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters

13

Fig.12.LineratiodiagnosticdiagramstoidentifyAGNs.TheleftpanelistheBPTplaneshowingtherelationbetweenfouremissionlines.ThedashedanddottedcurvesseparateAGNsfromstar-forminggalaxies(seetext).Theverticalandhorizontallinesaretheapproximateseparationbetweentypes.Thelowerrightpanelisthe[Oii]–HαdiagramaimedtoidentifyLINERs.ThedottedlineisthelocalKennicutt’srelationforstar-forminggalaxies,whereasthedashedlineisthetesttoidentifyLINERs.Theupperrightpanelistherelationbetween[Nii]andHαEWs.Blueopencirclesare“normal”star-forminggalaxiesandred lledonesaretheredstar-forminggalaxies.Thesizeofthesym-bolsisrelatedtothecon dencewithwhicheachindexcanbemeasured,thelargerthebetter.

WeplotinFig.12allgalaxiesforwhichthoseindexescanbemeasured.Thelinesaretheempiricalseparationbetweenstar-forminggalaxiesandAGNsofKau mannetal.(2003):

log

[Oiii]

log [Nii]

0.61Hβ

=

+1.19(3)

Hα 0.47

Theseparationbetweengalaxytypesismadeusing[Oiii]/Hβ>3and[Nii]/Hα>0.6,withthelatteralsousedindependentlyforallgalaxieswherethesetwolinesarepresent,whichoccurredmoreoftenthaninthecaseofthefourlinestest.ThelatesttestwasproposedbyYanetal.(2006).Itusesonlytheratiobetween[Oii]andHαEWsandwasaimedmainlytodetectLINERs.

W0([Oii])>5·W0(Hα) 7

(4)

Intotal,10galaxiesshowsomesignsofAGNactivitywith6beinggalaxiesclassi edas“redstar-forming”.Notethat,theemission-linedataforallAGNcandidatesarepositionedclosetotheboundariesoftherespectivetests,indicatedinFig.12,whichmeansthattheirnuclearactivityisratherloworcomposite.TheexclusionoftheseAGNscandidatesdoesnota ecttheresultsshowninFig.9and10,whichisanexpectedresultbecauseAGNfrequencyisnotcorrelatedwithenvironment(Milleretal.2003).

Asnotedbefore,inFig.9and10,themeanEWsofthe[Oii]andtheHαlinesdisplaysimilarvalues,eventhoughinlocalsamplestherelationbetweentheEWsoftheseemissionlinesfollowstheKennicutt’slaw(W1992).Thiscanbemoreclearly0([Oii])≈0.4Wseeninthe0(Hα),KennicuttlowerrightcornerofFig.12,wheretheKennicutt’srelationisplot-ted.Noclearexplanationhasbeenfoundforthisdeviation,butHammeretal.(1997)reportedthesamee ectintheCanada-FranceRedshiftSurveygalaxiesatsimilarredshifts.Theypre-sentedvarioushypothesesthatmayapplytoourwork,suchas,lowerextinction,lowermetallicitiesandcontaminationbyAGNs.However,weexcludethepossibilityofhereastrongAGNcontaminationandmostnormalstar-forminggalaxiesalsopresentthese“unusual”values.Thedeviationisthereforeprob-ablycausedbythelowermetallicitiespresentindistantgalaxies(seeKobulnicky&Kewley2004),becausethe[Oii]-Hαratiode-pendsstronglyonthisparameter(Jansenetal.2001).

WecanestimatethecontributionofdustextinctionusingtheTully&Fouque(1985)extinctionlawsfordiskgalaxies.Atz≈0.25,theVandI lterscorrespondapproximatelytorestframeBandR-bands.Atagiveninclinationangle,theextinctionintheR-bandis～0.56E(B):onlydiskgalaxieswithinclinationslargerthan60 willthereforehaveacorrectionfactorE(B R)>0.2mag(seeTable1inB¨ohmetal.2004),avaluesu cientlylargetomovetheirdata-pointsawayfromred-sequence.

Ourground-basedINTimagesdonotallowustosecurelyclassifythemorphologicalpropertiesofourgalaxies,sincethetypicalseeingof～1arcsec(～4kpcatz=0.25)repre-sentsapproximatelyonescale-lengthforspiralgalaxies(e.g.Bamfordetal.2007).Basicpropertiescanhoweverbeobtained,asgalaxiesinoursampletypicallyhaveanapparentsizeof5–10arcsec.Afterexamination,we ndthatoutofthe25“redstar-forming”galaxies,11areclearlyspirals,11appearbulge-dominated,twoareirregularandonegalaxy,whichisalsoanAGNcandidate,showssignsofinteraction.Outof11spirals,8areprobablyedge-ongalaxiesandtheremainingthree,face-on.

Dustextinctioncan,therefore,explainthecolorsofonlyafractionoftheredstar-formingobjects,becausedustpropertiesatz～0.25donotdi ermuchfromthoseofthelocaluniverse,andhighly-tiltedgalaxiescanbeeasilydistinguished.

Theredstar-forminggalaxiesappeartobetransitionob-jectspopulatingthe“greenvalley”(Salimetal.2007)inFig.13,whereweplotthespeci cstar-formation(sSFR)activity5versusstellarmass.Mostofthered-starforminggalaxies(aswellassomeAGNs)arelocatedina“transitionregion”6be-tweennormalstar-forminggalaxiesandpassiveones.ThemeansSFR10fornormalstar-forminggalaxiesis～(1.08±0.65)×10 yr 1,whereastheredstar-forminggalaxieshaveonaver-agesSFR≈(2.4±0.6)×10 11yr 1,aboutanorderofmag-nitudelower.TheaverageupperlimitforpassivegalaxiesissSFR≈(4.8±3.3)×10 12yr 1becausewedonotincludegalax-ieswithunphysicalstar-formationrates.

Wenotethatthosegalaxiesmayalsobepresentinthe eld,althoughwecannotclearlyidentifythem,giventheuncertaintiesinthek-correctionsof～0.2mag,whicharelargerthantypicalred-sequencescatter.However,itcanbeseenthatmostofthenormal eldandclusterstar-forminggalaxiesarelocatedintheupperpartofthisdiagram,aroundtherelationforlocalgalaxiesfoundintheUV-selectedsampleofSalimetal.(2007).Wenote

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

14Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25

clusters

Fig.13.Speci cstarformationratesfor eld(top)andclus-ter(bottom)galaxies,versusstellarmass.Normalstar-forminggalaxiesareplottedwithblue lledstarsandtheredstar-forminggalaxieswithgreenpentagons.Theredopenstarsarepassivegalaxieswith0<W0([Oii],Hα)<5andareshownforcompar-ison.TheblackcirclesaretheAGNcandidates.ThethicklineisthelocalrelationfromSalimetal.2007.

that eldandclusterstar-forminggalaxiesarelocatedinsimilarregionsofthisdiagram,anadditionalindicationthatbothpop-ulationsarecomposedsimilarclassesofobjects.However,theredstar-forminggalaxiesappeartobeclearlyo setfromthisrelation.

Itisinterestingtonotethatthede nitionofastar-forminggalaxysetatW0([Oii],Hα)≥5Ånotonlyhasaobservationalsensebut 11alsoaphysicalmeaningandcorrespondstoasSFR≈2×10yr 1,aratesu cientlylowtoconsideragalaxyaspassive.

Itispartofthestandardpictureofgalaxyevolutionthatob-jectsinthebluecloud(herethestar-formingsequence)slowlygrowinstellarmassviagasaccretionovercosmictimes.Mergersandotherstronginteractionscantriggerstar-bursts,dis-placingupwardsthegalaxiesinthediagram(Fig.13)addingalargeamountofstellarmassinashortperiodoftime(somovingrightwards).Ontheotherhand,gasexhaustionorgasremovalbymeansofinteractionsorfeedbackprocessescanleadtoaquenchingofstar-formationthatmovesthegalaxydownwards,towardstheredsequence,whereitcanexperiencesmallepisodesofstar-formation,accretemoregasandmoveagainintothebluecloud,orstaypermanentlythereiftheenvironmentishostile(asinthegalaxyclusterscores).

Inthispicture,theredstar-forminggalaxiesarelocatedinanintermediatestagebetweenthetwomainsubtypes,withlowerbutstillappreciableamountsofstar-formation.Thevariationintheabundanceofthispopulationwithcosmictimemayprovideadditionalinsightsintothenatureofthestellarmassbuildup,al-though,amorecarefultreatmentofAGNactivity,dustextinctionandstellarpopulationisrequiredtofullyexplaintheirnature.

8.Summaryandconclusions

WehaveobtainedMOSCAspectroscopyfor149membergalax-iesin6clustersat z ～0.25,outtolargeclustercentricdis-tances.Thissampleiscompareddirectlywith97galaxiesinthe eld.ThespectroscopicdatasetiscomplementedwithVandI-bandphotometryinthethree eldsandmultibandphotometryfromtheSDSSintwoofthem.Themain ndingscanbesum-marizedinthefollowing.

1.Thesuppressionofthestar-formationactivitycanbede-tectedatlargeclustercentricdistances(R>1R<10Mpc 1,inanenvironmentwherevirial)andlowdensitiesΣ5theclus-terissupposedtohavelittlein uence.Thisresultagreeswithsimilarresultsatredshiftz≈0basedonthe2dFGalaxyRedshiftSurvey(Lewisetal.2002)orSDSS(G´omezetal.2003),whereacriticalvalueofdensitywasfound,belowwhichtheenvironmentappeartobegintoplayacriticalrole.Althoughourdensityestimatesarenotdirectlycomparabletotheselow-redshiftstudies,itispossiblethatwedidnotreachthislowthresholdofΣ5～1Mpc 2reportedbythosestudies.Ourinvestigationreachedstar-formationactivitiesclosetothosefoundinthe eld,probingthetransitionbe-tween eldandclusterenvironmentinthedistantUniverse.Thedecreaseofthestar-formationactivityissmoothwithincreasingdensity,butamorecomplexbehaviorwasfoundwhentheradialdependenceisstudied,asitisstronglyaf-fectedbysubstructure.

2.Thetrendsinthestar-formationactivitymeasuredbythemean[Oii]andHαEWsareduemainlytoastrongde-creaseintherelativenumberofstar-forminggalaxiesto-wardshigherdensitiesandsmallerclustercentricdistances,ratherthanaslowdeclineinthestar-formationratesofgalaxies.This ndingfavorsviolentsuppressionofthestar-formationactivity.

3.Despitetheimportanceoftheoveralltrends,importantdif-ferencesarefoundbetweenthestudiedclusters.Thetwomostwell-studiedclusterswereanalyzedseparatelyfromallotherclusters..Itwasfoundthattheshapeofthestar-formationgradientswerequitedi erentfromeachother..Thisdi erencewasmoreaccentuatedintheradialtrendssincethee ectsofsubstructurecouldnotbediscernedintheassumedradialdensitypro le.

Intheliterature,manystudieshavefocusedeithersolelyononeusuallywell-sampledcluster(e.g.Kodamaetal.2001;Demarcoetal.2005;Sato&Martin2006),oronafamilyofclusters(selectedbyX-rayluminosity,redshiftrange,etc),generallyfarlesswell-sampled,whichtypicallycombinealldatatocreatea“composite-cluster”(e.g.Baloghetal.1999,2002a;Pimbbletetal.2006)inasimilarwaytoouranal-ysishere.However,ourstudyindicatesthatmanyoftheoveralltrendsmaynotbeuniversal,butmaybestronglyre-latedtotheparticularitiesofthesystemthattheindividualgalaxiesbelongto.Therefore,thee ectsofthesubstructureshouldnotbeneglectedwhenanalyzingtheuniversalityofstar-formation-environmentrelation,becauseeachparticularsystemmayhavedi erentproperties(seealsoRinesetal.2005forasimilarresultatz=0).

4.Theclustersshowvariationsnotonlyduetothesubstruc-ture,butalsointheirgalaxypopulations.Forexample,wedetectedanimportantsub-populationofredstar-forminggalaxiesinsomeclusters,whichhavesimilarcolorsorareredderthanthered-sequence.Thecharacteristicsofthispop-ulation,asmeasuredbytheirenvironmentaldistribution,donotdi ermuchfromtheremainderoftheemission-linepop-

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Verdugoetal.:Galaxypopulationsintheinfallingregionsofz≈0.25clusters15

ulation.AfractionofthemcouldbeAGNs,buttheAGNcontaminationisnotlargerthanintherestofthestar-formingpopulation.Nonetheless,allAGNcandidatesshowrelativelylowactivity.

Dustmayplayarolebecausesomegalaxiesareclearlyedge-onspirals.Thise ectmaybeopresentinothergalaxies.Itis,however,intriguingthatsomeotherwiseblueactivestar-forminggalaxieshavethepreciseamountofdusttomakethemfallontothenarrowredsequence.

Thesetwoe ectstogether,however,areonlyabletoexplainafractionofthispopulation.

Thesegalaxiesarelocatedinatransitionzone,betweennor-malstar-forminggalaxiesandpassiveones,wheregalaxiesappeartoformstarsatarelativelylowerrate.Theymaybeintheprocessofshuttingdowntheiractivityand/ortheycancontainarelativelysigni cantoldstellarpopulationcom-binedwithamoderateamountofdust.Ifthesegalaxiesaretrulytransitionobjects,theirabundancemayprovideimpor-tantcluesaboutthemass-assemblyhistoryasgalaxiesgrowinmassviaaccretionandmergingandshutdowntheirstar-formationovercosmictime(e.g.Belletal.2005).

Ourresultsfavormechanismsofstrongstar-formationsup-pression.Amongthepreferredprocessesisram-pressurestrip-ping(andotherstronggalaxyinteractionswithintheintraclus-termedium).Thisprocesscanquenchthestar-formationontimescaleasshortas1Gyr,whichisthedynamicaltimescaleofaclusterpassage.Ram-pressureisverye ectiveinthecen-tralregionsoftheclusters(e.g.Kapfereretal.2007).Wedetecthoweverstar-formationdepletionatclustercentricdistancesasfaras～3Rhavealreadyvirial.Itispossiblethatmanygalaxiesintheoutskirtspassedthroughthedenserintraclustermedia.Infact,modelsbyGilletal.(2005)predictthatasmanyashalfofthegalaxiesbetween1–2.5Rvirialmaybe“bouncing”aftera rstpassage(the“backsplash”scenario)andthushaveexperiencedstronginteractionsintheinnerclustercoreforasu cienttimetoexplaintheirpassivenature.Therefore,ram-pressurestrippingcannotdisregardedasaimportantmechanism,particularlybe-cause,sincedirectevidenceofthisprocessatworkhasbeenreportedbysomeauthors(e.g.Bosellietal.2006;Corteseetal.2007).

Otherprocessesmaybestillacting,becausequenchingofstar-formationisobservedatdistanceslargerthanthosepre-dictedbytheGilletal.(2005)simulations.Also,theirproposed“backsplash”populationwouldonlyaccountforafractionofthegalaxypopulationintheclusteroutskirts.Anyotherpro-cessthatquenchesthatstar-formationmoregradually(e.g.star-vation,harassment,etc)wouldhavebeendetectedviaenhance-mentordepletioninthestar-formingpopulationwithenviron-ment,whichisnotthecase.Onepossibilityisthatotherpro-cessesa ectthestar-formationongalaxiesbeforetheybegintofallintotheclusters,ingroupsand lamentsembeddedinthelarge-scalestructure.Inthoseenvironments,severalprocessesarethoughttobee ectiveinchangingthegalaxystellarpopula-tions.Ram-pressurestrippingmaystillbee ectiveinsystemsoflowermassesundercertaincertainconditions(e.g.Fujita2004;Hester2006)andthusmaycontribute.Mergerandtidalinterac-tionsinthoseenvironmentsarealsolikelyandtheycantriggerstarburststhatconsumegasrapidlyandstriptheremaininggasviafeedbackmechanisms(e.g.Bekki2001;Fujita2004).Thisscenarioiscompatiblewiththerecent ndingsofTanakaetal.(2007)andHainesetal.(2007).

Itisimportanttonotethateveryclusterisaparticularen-tityofitsownanditislikelythatdi erentprocessesareimpor-

tant.Theycandependontheclusterhistoryandcon guration,aswellasonthecharacteristicsofthesurroundingenvironment.Thesee ectsmayin uencethegalaxypopulationthatinhabittheclustersasshownrecentlybyMoranetal.(2007).Thisviewissupportedherebythedi erentstar-formationgradientsde-tected,duemainlytosubstructureandtheabundancesinthegalaxypopulation,withsomeclustersharboringanimportantfractionofred-starforminggalaxies,whichmaybeimportantinthegeneralschemeofgalaxyevolution.

Acknowledgements.Wethanktoananonymousrefereeforinsightfulsugges-tionsthathelpedtoimprovethispaper.WewouldliketothanktheCalarAltolocalsta fore cientsupportduringtheobservationsandD.Gilbankforpro-vidingINTimagingandphotometry.WethankK.J¨agerandA.Fritzforsoft-wareandobservationalsupport.WethankM.Balogh,C.DaRochaandJ.Rasmussenforhelpfuldiscussions.Thisworkhasbeen nanciallysupportedbytheVolkswagenFoundation(I/76520)andtravelgrantstoCalar-AltobyDFG(ZI663/5-1).

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AppendixA:Starformationrates

Allindicatorsofstar-formationrates(SFRs)havetheirownbiasandsystematicsduetothedi erentprocessestracedfor

each

ofthem(forarecentreviewseeMoustakasetal.2006).Intheoptical,atleasttwoe ectsareveryimportant:extinctionandmetallicity.Ontheotherhand,opticalSFRscalculationrequiresaccurate uxcalibration,thatwelack.Howeverwecanstilles-timateSFRsusingtheEWsandtheabsolutemagnitudes(calcu-latedinSect.2.8)asaproxyofthecontinuum ux.Fortunately,ourspectracoverboth[Oii]andHαlines,sobothresultscanbecompared.

For[Oii]derivedSFRs,wecantakethecalibratedrelationofKennicutt(1992)SFR([Oii])=3.4×10 12

LB

L(A.3)

C

whereLCisthecontinuumluminosityinergs 1Å 1

(seeLewisetal.2002)andLdeterminedCby≈LBlantonR.ForaL galaxy,Letal.(2001),C=1.1×1040

ergss 1,aswithM

.8mag,leaving:

R= 21L(Hα)=1.1×1040W

0(Hα)10 0.4(MR MR)[ergss 1].(A.4)

Therefore, nallywehave

SFR(Hα)=0.079W0(Hα)10 0.4(MR+21.8)[ergss 1].

(A.5)

WeobtainedSFRsforallgalaxiesinwhicheitherofthesetwolinesismeasurable.Bothwaysarelikelytohavesystemat-icsanduncertainties,[Oii]becauseitisacalibratedrelationanddoubtspersistaboutitsuniversality(e.g.Hammeretal.1997).Alsoitisstronglya ectedbydustandmetallicity.InthecaseofHα,theassumptionsheremade,introduceuncertaintiesabouttheaccuracyofthe ux.Therefore,wetaketheaverageoftheSFRobtainedfrom[Oii]andHαandwhenonlyonelineispresentwetakethisvalue.WedidobtainSFRsforgalaxiescon-sideredpassive,howeverthosevaluesprobablyhavelargerun-certainties,sotheirSFRscanbeconsideredasanupperlimit.WealwaysmakedistinctionofbothpopulationsbasedintheEWdistinction(seeSect.2.7).WedidnotattempttoobtainSFRsforgalaxieswithnegativeequivalentwidthsbecausetheyyieldtounphysicalvalues,di culttointerpreteifincluded.

Usingthestellarmassesobtainedwithkcorrect(seeSect.2.8)weobtainedthespeci cstarformationrates(sSFR).ItisremarkablethestrongcorrelationwithlittlescatterbetweenEWsandsSFR,obtainedineitherway(i.e.[Oii]andHα)andthelittlescatter(albeitlargerfor[Oii]),aswellasthesimilarvaluesdisplayedusingbothmethods(seeFig.A.1),despitetheroughestimationmadehere.Also,itisimportantthatbothindicatorsyieldsimilarvaluesastheHαlinebecomesinaccessibleatlargerredshiftsandonly[Oii]canbeused.

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

OnlineMaterial

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

Table3.Dataforindividualobjects.Weonlypresentgalaxiesforwhichweobtainedsecuredredshifts(seesection2.4).Notethatweincludeallobjectsforwhichwewereabletoobtainthefollowingparameters.Manyobjectswereexcludedintheanalysisinordertoobtainahomogeneoussample(seesections3.5&4.4).Thecolumnsarethefollowing.Column(1):ObjectID.Column(2):cluster,groupor eldmembership.Columns(3)and(4):J2000skycoordinates.Column(6):redshift.Column(7):TheI-bandmagnitude.Column(8):TheV Icolor.Columns(8)and(9):TheabsolutemagnitudesintherestframeBandR-bands.Column(10):Thelogarithmofthestellarmass.Columns(11)and(12):The[Oii]EWsanderrors.Columns(13)and(14):TheHαEWsanderrors.

(1)(2)

(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)IDmembership

RA

DEC

z

I

V-IMBMRlog(M)[Oii]E([Oii])

HαE(Hα)[mag]

[mag]

[mag]

[mag]

[Mr2211

⊙ ][Å][Å][Å][Å]08vmf194

17:29:19.77

74:41:11.2

0.21167

16.75

1.426

-21.42

-22.79

10.78

8.95

0.95

1.10

0.23

r2211

10vmf194

17:29:30.06

74:40:43.0

0.21107

18.54

1.422

-19.64

-21.01

10.06

0.18

0.55

1.13

0.24

r2212

08vmf194

17:29:22.55

74:40:52.3

0.21080

17.92

1.409

-20.27

-21.62

10.30

3.93

0.60

1.12

0.28

r2212

14vmf194

17:26:24.27

74:27:35.2

0.20877

17.66

1.321

-20.62

-21.85

10.37

-0.02

0.69

-10.33

0.30

r2221

03bxdcs220

17:26:50.87

74:34:08.8

0.26652

19.52

0.880

-19.83

-20.66

9.75

-61.16

1.72

-45.71

1.66

r2221

03xdcs220

17:26:17.74

74:34:09.3

0.25712

18.85

1.587

-19.68

-21.19

10.17

0.21

0.39

-0.91

0.17

r2222

05xdcs220

17:24:11.04

74:31:12.1

0.26144

18.58

1.441

-20.16

-21.52

10.27

4.80

0.35

3.06

0.23

r2241

07xdcs220

17:23:28.45

74:43:41.7

0.25977

17.00

1.572

-21.59

-23.09

10.92

5.64

0.45

1.65

0.17

r2241

10xdcs220

17:23:24.29

74:42:56.2

0.25953

17.99

1.518

-20.64

-22.10

10.52

8.83

0.64

2.30

0.20

r2241

18xdcs220

17:23:05.48

74:39:30.5

0.25451

18.38

2.567

-19.55

-21.63

10.43

-20.46

0.29

-35.91

0.28

r2242

04xdcs220

17:24:12.22

74:22:23.8

0.26246

18.92

0.879

-20.37

-21.24

9.98

-37.27

1.09

-47.44

0.77

xdc29

14vmf131

13:11:22.18

32:28:53.8

0.29902

19.24

1.613

-19.75

-21.26

10.19

0.98

0.30

0.35

0.20

r2621

16vmf131

13:11:24.66

32:28:36.9

0.30015

18.99

1.340

-20.24

-21.50

10.23

-20.84

0.24

-31.54

0.33

r2631

02vmf131

13:10:16.57

32:30:36.6

0.29501

18.70

1.719

-20.14

-21.75

10.41

2.09

0.23

-1.66

0.16

r2632

03vmf131

13:10:18.96

32:30:18.7

0.29380

18.47

1.693

-20.38

-21.97

10.49

-0.38

0.18

0.15

0.13

r2632

12vmf131

13:10:34.20

32:27:30.8

0.29464

19.21

1.024

-20.25

-21.22

10.02

-19.41

0.21

-27.83

0.33

r2632

04vmf131

13:10:17.22

32:19:51.8

0.29577

18.90

1.903

-19.78

-21.56

10.36

-2.01

1.15

-12.32

0.90

r2641

06vmf131

13:10:12.94

32:24:09.1

0.29574

18.59

0.864

-21.02

-21.84

10.21

2.78

0.52

1.22

0.30

r2641

12vmf131

13:10:01.42

32:23:48.2

0.29614

17.98

1.500

-21.07

-22.47

10.65

....

....

-0.36

0.39

r2651

17vmf13113:11:13.9832:19:10.50.2943817.541.744-21.27-22.9010.87-4.270.17-0.600.11r265107vmf13113:10:05.7232:21:12.20.2965118.321.105-21.08-22.1310.425.070.800.240.60ba12vmf13113:09:55.0532:21:49.00.2938218.471.684-20.39-21.9710.493.510.553.180.36ba18vmf13113:10:11.3832:22:02.30.2938818.151.666-20.74-22.2910.616.150.490.200.35ba28vmf13113:09:56.1132:22:16.80.2920716.721.718-22.10-23.7011.185.120.350.840.22ba36vmf13113:10:00.1832:22:59.40.2943118.231.361-20.93-22.2110.52-6.820.38-11.690.35ba39vmf13113:09:57.6832:23:13.00.2923317.951.708-20.88-22.4710.69-2.660.46-0.460.31r2611

13vmf132

13:11:51.74

32:33:29.2

0.24964

17.79

1.463

-20.81

-22.20

10.54

6.78

0.35

1.40

0.21

r2611

02vmf132

13:12:27.01

32:32:06.6

0.24855

18.53

1.497

-20.01

-21.44

10.25

-15.32

0.23

-10.12

0.13

r2612

06vmf132

13:12:10.39

32:30:03.0

0.24954

17.28

1.477

-21.30

-22.70

10.74

1.87

0.14

0.97

0.09

r2612

03vmf132

13:11:01.05

32:30:41.6

0.24128

18.35

1.479

-20.12

-21.54

10.29

1.20

0.21

1.89

0.12

r2621

11vmf132

13:11:13.29

32:28:50.9

0.23976

18.63

1.575

-19.73

-21.24

10.19

4.32

0.27

1.15

0.13

r2621

22vmf132

13:11:33.84

32:29:11.9

0.25032

18.17

1.536

-20.36

-21.83

10.41

-2.56

0.23

-4.01

0.13

r2631

08vmf132

13:10:25.08

32:28:44.7

0.25008

19.30

1.361

-19.41

-20.70

9.92

....

....

-1.35

0.28

r2632

13vmf13213:10:37.8232:27:15.20.2456618.341.486-20.19-21.6010.31-0.170.191.180.12r264129vmf13213:09:49.9932:22:41.00.2495419.770.784-19.55-20.259.52-53.591.20-61.712.16r2811

16vmf73

09:43:58.38

16:41:09.6

0.25266

16.96

1.438

-21.70

-23.04

10.87

-0.16

0.65

-2.47

0.24

r2811

19vmf73

09:43:58.81

16:40:02.3

0.25384

18.60

1.386

-20.12

-21.42

10.22

-1.26

2.62

0.70

0.67

r2811

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

(1)IDr2811

25r2812

09r2812

14r2821

08r2821

17r2821

20r2821

27r2821

01r2822

04r2822

06r2822

14r2822

16r2822

19r2822

22r2822

25r2831

10r2831

07r2841

17r2851

14r2851

01r2811

05r2811

08r2811

11r2811

14r2811

23r2812

16r2812

22r2812

03r2821

07r2821

10r2821

07r2822

13r2831

20r2841

08r2841

09r2851

11r2851

09r2222

18r2222

08r2221

18

group2

17:26:45.45

74:27:01.2

0.04405

19.21

0.657

-16.34

-16.92

8.06

....

....

-51.86

0.39

group2

17:27:07.02

74:30:29.4

0.04385

18.36

0.940

-16.73

-17.57

8.48

....

....

-41.37

0.46

group1

17:25:26.20

74:30:15.5

0.05219

17.48

0.835

-18.12

-18.89

8.98

....

....

-9.51

0.12

group1

17:26:29.54

74:29:34.7

0.05308

16.30

1.114

-18.89

-19.96

9.52

....

....

-13.81

0.16

vmf74

09:43:52.55

16:31:20.4

0.18176

19.32

1.128

-18.84

-19.87

9.52

-39.42

1.39

-65.98

1.24

vmf74

09:43:50.52

16:30:28.0

0.18124

19.09

1.184

-19.00

-20.10

9.63

0.54

2.14

-0.59

0.77

vmf74

09:44:40.09

16:30:59.7

0.18478

19.32

1.081

-18.93

-19.93

9.52

-21.39

1.97

-28.51

0.92

vmf74

09:42:44.14

16:45:34.9

0.17989

18.08

1.173

-19.99

-21.06

10.00

-5.48

1.19

-2.32

0.60

vmf74

09:43:39.73

16:37:22.5

0.17946

19.23

1.161

-18.85

-19.89

9.54

1.35

1.87

-14.50

0.45

vmf74

09:43:49.72

16:40:51.4

0.18048

17.63

1.306

-20.28

-21.51

10.23

4.17

0.58

1.07

0.15

vmf74

09:43:46.04

16:39:54.5

0.17763

18.76

1.285

-19.11

-20.33

9.76

-16.78

7.64

1.04

1.10

vmf74

09:43:50.04

16:39:54.7

0.17926

18.60

1.319

-19.27

-20.49

9.83

-3.49

4.05

2.84

0.91

vmf74

09:43:56.38

16:39:57.5

0.17992

18.21

1.239

-19.77

-20.92

9.97

10.57

3.86

-0.03

0.71

vmf74

09:43:43.45

16:44:31.8

0.18096

17.77

1.289

-20.18

-21.39

10.18

8.73

3.08

0.07

0.36

vmf74

09:44:01.02

16:42:04.1

0.17750

17.95

1.203

-20.03

-21.16

10.07

-16.80

4.23

-10.69

0.60

vmf74

09:43:59.52

16:38:29.8

0.17833

17.98

1.123

-20.12

-21.14

10.02

-2.49

0.96

-6.81

0.28

vmf74

09:43:58.75

16:42:02.5

0.18250

17.82

1.305

-20.11

-21.34

10.16

5.52

1.71

1.56

0.36

vmf74

09:43:49.12

16:43:21.2

0.18086

16.81

1.354

-21.03

-22.33

10.57

0.70

0.64

-1.23

0.18

vmf74

09:43:45.15

16:44:05.6

0.17884

18.53

1.268

-19.40

-20.56

9.84

-8.10

1.85

-8.58

0.53

vmf74

09:43:44.49

16:44:54.2

0.18009

18.50

1.183

-19.57

-20.65

9.85

-21.52

1.18

-77.27

1.12

vmf74

09:43:44.47

16:46:05.3

0.17837

17.66

1.323

-20.18

-21.42

10.20

4.45

0.72

1.37

0.24

vmf73

09:44:04.69

16:32:49.3

0.25340

19.02

1.446

-19.63

-20.98

10.05

3.75

2.19

-4.63

0.66

vmf73

09:44:23.76

16:31:47.1

0.25035

18.12

1.383

-20.57

-21.88

10.39

1.61

0.98

1.43

0.22

vmf73

09:44:41.05

16:29:19.5

0.25003

18.64

1.176

-20.27

-21.37

10.14

-45.76

2.52

-21.50

0.73

vmf73

09:43:08.02

16:42:45.4

0.25696

18.24

1.102

-20.78

-21.80

10.28

-10.66

1.02

-18.04

0.78

vmf73

09:43:22.06

16:39:07.9

0.25037

18.54

1.402

-20.14

-21.46

10.24

-1.78

0.67

-4.66

0.26

vmf73

09:43:25.34

16:39:07.2

0.25491

17.81

1.494

-20.81

-22.24

10.57

2.17

0.52

0.26

0.17

vmf73

09:43:30.57

16:38:56.0

0.25294

19.30

1.418

-19.38

-20.69

9.93

2.32

1.27

3.04

0.48

vmf73

09:43:36.80

16:41:02.7

0.25521

18.19

1.427

-20.50

-21.87

10.41

0.76

0.82

0.47

0.25

vmf73

09:43:38.75

16:38:55.5

0.25331

18.59

1.415

-20.09

-21.41

10.22

3.89

0.90

2.31

0.29

vmf73

09:43:51.72

16:41:45.0

0.25285

18.03

1.186

-20.89

-21.96

10.37

-2.82

0.50

-16.58

0.30

vmf73

09:43:55.89

16:40:36.0

0.25507

18.68

1.394

-20.05

-21.38

10.21

0.97

1.08

2.27

0.32

vmf73

09:43:58.93

16:39:22.0

0.25607

18.91

1.398

-19.81

-21.14

10.11

-0.27

0.96

1.26

0.34

vmf73

09:43:23.53

16:39:46.4

0.25767

17.98

1.298

-20.85

-22.09

10.45

-0.29

1.31

-3.83

0.54

vmf73

09:43:33.63

16:39:06.8

0.25295

17.80

1.467

-20.83

-22.19

10.54

-13.73

2.82

3.80

0.80

vmf73

09:43:36.34

16:36:57.3

0.25693

17.58

1.503

-21.04

-22.46

10.65

3.38

2.29

-2.92

0.58

vmf73

09:43:48.71

16:40:39.1

0.25456

17.87

0.823

-21.45

-22.22

10.33

-33.96

0.81

-69.22

1.50

vmf73

09:43:53.57

16:41:43.2

0.25292

17.19

1.430

-21.47

-22.80

10.77

1.48

1.28

1.53

0.28

vmf73

09:44:00.32

16:40:11.5

0.24866

18.70

1.319

-20.03

-21.27

10.14

5.74

3.73

-1.70

0.82

vmf73

09:43:59.68

16:37:30.1

0.25423

18.10

1.536

-20.47

-21.93

(2)

membership

(3)RA

(4)DEC

(5)z

(6)I

[mag]

(7)V-I[mag]

(8)MB[mag]

(9)MR[mag]

(10)log(M )[M⊙]10.46

(11)[Oii][Å]-5.85

(12)E([Oii])

[Å]1.51

(13)Hα[Å]-2.06

(14)E(Hα)[Å]0.46

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

(1)IDr2231

19r2211

13r2211

19r2211

21r2212

18r2621

16r2631

01r2632

01r2211

04r2211

15r2211

18r2211

24r2212

14r2212

19r2221

13r2222

02r2222

05r2222

08r2222

12r2222

15r2222

06r2231

11r2231

16r2231

02r2241

11r2241

20r2241

22r2242

07r2242

11r2242

13r2251

06r2251

10r2251

15r2251

02r2611

07r2611

16r2612

03r2612

11r2612

14r2612

02

eld

13:10:57.07

32:28:05.7

0.12024

18.68

1.209

-18.33

-19.57

9.51

-1.12

0.60

-10.26

0.13

eld

13:11:52.16

32:32:12.1

0.44078

18.83

2.091

-21.50

-22.91

10.86

2.98

0.21

-5.77

0.32

eld

13:12:01.09

32:31:31.0

0.43522

19.02

2.049

-21.37

-22.91

10.92

1.11

0.22

1.50

0.37

eld

13:12:18.72

32:30:40.0

0.49186

19.47

1.650

-21.44

-22.44

10.39

-12.58

0.18

....

....

eld

13:11:46.33

32:32:54.9

0.35143

18.08

1.796

-21.23

-22.78

10.83

3.52

0.33

3.01

0.31

eld

13:12:02.58

32:31:35.8

0.43572

18.12

2.142

-21.96

-23.59

11.15

1.37

0.36

-1.01

0.55

eld

13:12:15.56

32:33:06.4

0.26403

18.93

1.349

-20.04

-21.39

10.17

-8.30

0.40

-23.45

0.37

eld

17:24:45.55

74:15:44.8

0.06325

18.35

0.743

-17.81

-18.51

8.77

....

0.00

-11.96

0.30

eld

17:24:04.79

74:18:39.2

0.44273

18.39

0.822

-22.37

-23.16

10.67

-5.02

0.14

-21.15

0.35

eld

17:23:50.15

74:20:50.9

0.05868

18.68

0.877

-17.14

-17.94

8.61

....

0.00

-26.72

0.30

eld

17:23:17.51

74:40:37.5

0.18069

18.01

1.095

-20.18

-21.18

10.02

-5.53

0.39

-21.72

0.21

eld

17:24:02.24

74:42:37.0

0.33906

18.85

1.709

-20.46

-22.00

10.49

-0.95

0.99

-3.18

0.40

eld

17:23:37.38

74:43:40.0

0.29567

18.02

1.610

-20.93

-22.43

10.66

1.50

0.67

0.67

0.25

eld

17:23:47.22

74:38:01.9

0.24012

17.91

1.212

-20.84

-21.98

10.39

2.47

0.58

1.78

0.18

eld

17:23:50.33

74:38:39.8

0.04373

18.69

1.516

-15.32

-16.93

8.48

....

....

-11.48

0.19

eld

17:23:55.07

74:42:40.0

0.33892

18.45

1.800

-20.79

-22.40

10.66

-9.00

0.91

0.97

0.44

eld

17:23:27.27

74:46:43.8

0.44623

18.36

2.172

-21.68

-23.40

11.09

4.18

0.47

....

....

eld

17:25:12.29

74:29:40.6

0.29537

19.17

1.210

-20.12

-21.26

10.11

-19.73

0.31

-48.69

0.45

eld

17:24:37.73

74:30:13.6

0.18489

19.49

1.168

-18.65

-19.75

9.49

-48.04

0.78

-32.86

0.40

eld

17:24:14.39

74:29:43.0

0.21837

19.06

0.920

-19.78

-20.61

9.73

-25.41

0.51

-26.11

0.43

eld

17:26:10.37

74:29:09.5

0.18043

18.17

1.046

-20.08

-21.02

9.94

-25.86

0.34

-29.13

0.18

eld

17:26:53.67

74:29:57.5

0.54749

19.25

2.087

-21.61

-23.16

10.95

-3.17

0.47

....

....

eld

17:26:54.96

74:31:35.9

0.27059

18.07

1.020

-21.16

-22.14

10.41

-0.55

0.24

10.24

0.62

eld

17:27:22.22

74:32:27.3

0.24178

19.18

0.881

-19.94

-20.76

9.78

-18.68

0.31

-19.77

0.22

eld

17:27:26.70

74:34:42.8

0.18050

19.03

1.057

-19.21

-20.16

9.60

-70.67

1.25

-13.85

0.18

eld

17:26:25.30

74:27:56.1

0.22819

18.78

1.348

-19.70

-20.96

10.03

-8.97

1.04

-15.25

0.47

eld

17:30:18.14

74:41:44.4

0.33812

18.31

1.818

-20.91

-22.54

10.73

2.78

0.72

-3.66

0.65

eld

17:29:50.08

74:42:24.7

0.24585

17.73

1.429

-20.86

-22.22

10.55

-6.09

0.50

-5.65

0.25

eld

17:30:45.34

74:41:21.3

0.31546

18.73

1.589

-20.44

-21.91

10.45

0.20

0.46

2.05

0.41

eld

17:30:05.41

74:40:00.7

0.15708

18.60

1.324

-18.97

-20.17

9.69

....

....

-3.98

0.41

eld

17:29:53.77

74:39:44.1

0.15745

17.39

1.226

-20.31

-21.42

10.15

....

....

-6.20

0.25

eld

17:29:01.00

74:40:07.9

0.27259

18.76

1.594

-19.96

-21.47

10.28

6.43

0.75

-6.25

0.30

eld

17:28:35.55

74:43:18.4

0.32074

18.43

1.319

-21.01

-22.24

10.52

-10.68

0.38

-15.00

0.40

group4

13:10:09.80

32:29:44.2

0.18593

18.05

1.416

-19.91

-21.28

10.20

2.90

0.38

0.17

0.18

group4

13:10:37.26

32:26:37.6

0.18599

17.17

1.017

-21.14

-22.14

10.26

-20.02

0.25

-27.48

0.30

group3

17:24:31.58

74:37:39.2

0.24194

18.17

1.709

-20.06

-21.72

10.41

-13.17

1.00

-2.97

0.21

group3

17:30:16.74

74:42:26.8

0.24230

18.69

1.510

-19.76

-21.21

10.17

5.14

0.64

3.05

0.24

group3

17:30:09.69

74:42:44.1

0.24513

18.45

1.431

-20.14

-21.49

10.25

-6.01

0.45

-4.50

0.21

group3

17:29:48.60

74:42:15.0

0.24404

17.93

1.503

-20.56

-21.99

10.47

3.07

1.35

2.55

0.38

group2

17:25:34.22

74:28:54.1

0.04133

17.43

0.962

-17.42

-18.34

(2)

membership

(3)RA

(4)DEC

(5)z

(6)I

[mag]

(7)V-I[mag]

(8)MB[mag]

(9)MR[mag]

(10)log(M )[M⊙]8.81

(11)[Oii][Å]....

(12)E([Oii])

[Å]

....

(13)Hα[Å]-8.52

(14)E(Hα)[Å]0.11

We conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of six different clusters, which differ in intrinsi

(1)IDr2621

06r2621

10r2621

18r2631

03r2631

05r2631

01r2632

05r2632

14r2632

11r2651

03r2651

07r2651

11r2651

13r2651

12ar2812

23r2812

26r2821

23r2821

24r2831

08r2831

16r2831

18r2841

09r2841

13r2841

19ar2851

06r2851

eld

09:44:07.29

16:29:22.8

0.23247

17.24

1.355

-21.25

-22.70

10.73

1.15

0.69

-1.32

0.17

eld

09:44:20.04

16:30:28.5

0.23338

17.51

1.290

-21.03

-22.49

10.63

-2.40

0.47

-3.95

0.15

eld

09:44:32.35

16:28:34.4

0.15980

18.91

1.039

-18.87

-20.08

9.47

-8.75

1.07

....

....

eld

09:44:38.51

16:27:52.5

0.23310

17.25

1.330

-21.14

-22.58

10.74

1.08

0.92

-3.37

0.23

eld

09:42:51.23

16:41:08.8

0.23352

17.07

1.118

-21.63

-22.86

10.70

-5.96

0.39

-22.38

0.31

eld

09:42:56.10

16:41:13.4

0.23116

18.63

1.252

-20.17

-21.21

9.79

-9.85

1.60

-20.22

0.95

eld

09:43:12.49

16:44:30.0

0.17047

17.87

1.241

-19.84

-21.31

10.25

....

....

-8.77

0.62

eld

09:43:23.20

16:40:38.3

0.16715

18.83

1.230

-18.89

-20.24

9.70

-21.56

1.01

-28.55

0.41

eld

09:43:28.76

16:37:53.2

0.18995

18.08

1.182

-20.06

-21.27

10.19

0.77

2.50

3.92

1.62

eld

09:43:51.93

16:45:45.2

0.21565

19.33

1.746

-18.67

-20.54

9.73

....

....

-0.58

1.05

eld

09:43:55.30

16:44:48.9

0.16487

18.46

1.398

-19.09

-20.51

9.91

12.44

7.53

4.62

0.50

eld

09:43:58.66

16:43:04.5

0.16614

18.56

0.943

-19.73

-20.44

9.39

....

....

-45.42

1.74

eld

13:11:07.05

32:17:24.8

0.40657

18.66

2.031

-21.48

-22.96

10.85

2.88

0.24

....

....

eld

13:10:59.78

32:18:39.0

0.40701

18.66

1.716

-21.32

-22.73

10.76

-3.53

0.18

....

....

eld

13:10:46.66

32:21:16.7

0.30771

18.66

1.317

-20.69

-22.01

10.44

0.53

0.18

0.38

0.17

eld

13:10:40.07

32:20:47.8

0.55177

18.00

1.669

-23.20

-24.32

11.22

-14.19

0.11

....

....

eld

13:10:03.30

32:21:30.2

0.28419

18.66

1.508

-20.38

-21.83

10.44

-13.38

1.20

-39.16

2.26

eld

13:10:38.86

32:28:04.1

0.30783

19.37

1.571

-19.69

-21.14

10.06

-23.37

1.36

-16.20

1.24

eld

13:10:23.46

32:29:52.4

0.40813

19.41

1.099

-20.92

-21.75

10.00

-36.95

0.27

....

....

eld

13:10:09.53

32:26:28.6

0.12557

18.07

1.184

-19.04

-20.25

9.73

....

....

....

....

eld

13:10:19.66

32:29:34.4

0.25985

18.90

1.514

-20.00

-21.00

9.75

-57.95

1.65

-8.50

0.40

eld

13:10:16.97

32:29:06.1

0.12306

16.99

1.228

-20.25

-21.28

10.02

....

....

-11.70

0.27

eld

13:11:28.25

32:28:06.1

0.43404

18.58

2.144

-21.45

-23.28

11.03

-4.27

0.23

....

....

eld

13:11:12.39

32:32:06.0

0.30175

18.37

1.359

-21.15

-22.32

10.49

-9.52

0.17

-12.55

0.16

eld

13:11:05.84

32:29:57.6

0.30678

18.87

1.875

-19.98

-21.76

(2)

membership

(3)RA

(4)DEC

(5)z

(6)I

[mag]

(7)V-I[mag]

(8)MB[mag]

(9)MR[mag]

(10)log(M )[M⊙]10.45

(11)[Oii][Å]-3.45

(12)E([Oii])

[Å]0.27

(13)Hα[Å]-1.38

(14)E(Hα)[Å]0.17

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