A&A585,A160(2016) Astronomy DOI:10.1051/0004-6361/201527399 & (cid:2)c ESO2016 Astrophysics CLASH-VLT: Environment-driven evolution of galaxies (cid:2) in the z = 0.209 cluster Abell 209 M.Annunziatella1,2,A.Mercurio3,A.Biviano2,M.Girardi1,2,M.Nonino2,I.Balestra2,P.Rosati4, G.BartoschCaminha4,M.Brescia3,R.Gobat5,C.Grillo6,M.Lombardi7,B.Sartoris1,2,8,G.DeLucia2,R.Demarco9, B.Frye10,A.Fritz11,J.Moustakas12,M.Scodeggio11,U.Kuchner13,C.Maier13,andB.Ziegler13 1 DipartimentodiFisica,Univ.degliStudidiTrieste,viaTiepolo11,34143Trieste,Italy e-mail:annunziatella@oats.inaf.it 2 INAF−OsservatorioAstronomicodiTrieste,viaG.B.Tiepolo11,34131Trieste,Italy 3 INAF−OsservatorioAstronomicodiCapodimonte,viaMoiariello16,80131Napoli,Italy 4 DipartimentodiFisicaeScienzedellaTerra,Univ.degliStudidiFerrara,viaSaragat1,44122Ferrara,Italy 5 KoreaInstituteforAdvancedStudy,KIAS,85Hoegiro,130-722Dongdaemun-guSeoul,RepublicofKorea 6 DarkCosmologyCentre,NielsBohrInstitute,UniversityofCopenhagen,JulianeMariesVej30,2100Copenhagen,Denmark 7 DipartimentodiFisica,UniversitàdegliStudidiMilano,viaCeloria16,20133Milan,Italy 8 INFN,SezionediTrieste,viaValerio2,34127Trieste,Italy 9 DepartmentofAstronomy,UniversidaddeConcepción,Casilla160-C,Concepción,Chile 10 StewardObservatory/DepartmentofAstronomy,UniversityofArizona,933NCherryAve,Tucson,AZ,USA 11 INAF−IASF-Milano,viaBassini15,20133Milano,Italy 12 SienaCollege/DepartmentofAstronomy,515LoudonRoad,Loudonville,NY,USA 13 UniversityofVienna,DepartmentofAstrophysics,Türkenschanzstr.17,1180Wien,Austria Received18September2015/Accepted14October2015 ABSTRACT Context.Theanalysisofgalaxyproperties,suchasstellarmasses,colors,sizesandmorphologies,andtherelationsamongthemand theenvironment,inwhichthegalaxiesreside,canbeusedtoinvestigatethephysicalprocessesdrivinggalaxyevolution. Aims.WeconductathoroughstudyoftheclusterA209withanewlargespectro-photometricdatasettoinvestigatepossibleenviron- mentaleffectsongalaxypropertiesthatcanprovideinformationongalaxyevolutioninclusterhostileenvironments. Methods.We use the dataset obtained as part of the CLASH-VLTspectroscopic survey, supplemented with Subaru/SuprimeCam high-quality imaging in BVRIz-bands,which yields 1916 cluster members (50% of them spectroscopically confirmed) down to a stellarmassM(cid:2) = 108.6M(cid:3).Wedeterminethestellarmassfunctionofthesegalaxiesindifferentregionsofthecluster,byseparating thesampleintostar-formingandpassiveclustermembers.Wethendeterminetheintra-clusterlightanditsproperties.Wealsoderive theorbitsoflow-(M(cid:2) ≤ 1010.0M(cid:3))andhigh-mass(M(cid:2) > 1010.0M(cid:3))passivegalaxiesandstudytheeffectoftheenvironmentonthe mass-sizerelationofearly-typegalaxies,selectedaccordingtotheirSérsicindex;theeffectsarestudiedseparatelyforthegalaxiesin eachmassrange.Finally,wecomparetheclusterstellarmassdensityprofilewiththenumberdensityandtotal-massdensityprofiles. Results.The stellar mass function of the star-forming cluster galaxies does not depend on the environment. The slope found for passivegalaxiesbecomesflatterinthedensestclusterregion,whichimpliesthatthelow-masscomponent startstodominatewhen movingawayfromtheclustercenter. Thecolor distributionoftheintra-clusterlightisconsistent withthecolor ofpassivecluster members.Theanalysisofthedynamicalorbitsofpassivegalaxiesshowsthatlow-massgalaxieshavetangentialorbits,avoidingsmall pericentersaroundtheBCG.Themass-sizerelationoflow-masspassiveearly-typegalaxiesisflatterthanthatofhigh-massgalaxies, and itsslope isconsistent with the slope of the relation of field star-forming galaxies. Low-mass galaxies are also more compact withinthescaleradiusof0.65Mpc.Theratiobetweenthestellarandnumberdensityprofilesshowsamasssegregationeffectinthe clustercenter.Thecomparativeanalysisofthestellarandtotaldensityprofilesindicatesthatthiseffectisduetodynamicalfriction. Conclusions.Our results are consistent with a scenario in which the “environmental quenching” of low-mass galaxies is due to mechanisms such as harassment out to r , starvation, and ram-pressure stripping at smaller radii. This scenario is supported by 200 the analysis of the mass function, of the dynamical orbits and of the mass-size relation of passive early-type galaxies in different clusterregions.Moreover,ouranalysessupporttheideathattheintra-clusterlightisformedthroughthetidaldisruptionofsubgiant (M(cid:2) ∼ 109.5−10.0M(cid:3))galaxies.Infact,ourresultssuggestthatlow-massgalaxiesaredestroyedbytidalinteractions,andthatthose thatavoidsmallpericentersaroundtheBCGareinfluencedbytidalinteractionsthatreducetheirsizes.Wesuggestdynamicalfriction astheprocessresponsiblefortheobservedmasssegregation. Key words.galaxies:luminosityfunction,massfunction–galaxies:clusters:general –galaxies:clusters:individual: Abell209– galaxies:stellarcontent–galaxies:structure–galaxies:evolution 1. Introduction environmental(i.e.nurture)processesplayakeyroleintheevo- lution of galaxies (Boselli & Gavazzi 2014) especially at the Galaxies in clusters experience many different processes, low-massend.Thesemechanismscanbedividedintotwomain that affect their properties and evolution. Among them the classes:gravitationalinteractions,whichincludeallsortsoftidal (cid:2) Based in large part on data collected at the ESO VLT (prog. interactions, e.g. galaxy-galaxy mergers, dynamical friction, and harassment and hydrodynamicinteractions, which include ID186.A-0798),attheNASAHST,andattheNASJSubarutelescope. ArticlepublishedbyEDPSciences A160,page1of17 A&A585,A160(2016) interactionsbetweenthegalaxy’sinterstellarmedium(ISM)and Table1.MainpropertiesoftheclusterAbell209. thehotintergalacticmedium,i.e.rampressure(forareviewsee Biviano2008).Theseprocessesareeffectiveindifferentregions BCG(α,δ) 01h31m52s.54,−13◦36(cid:7)40(cid:7).(cid:7)4 of the cluster (e.g. Treu et al. 2003; Boselli et al. 2006).Their MeanredshJi2f0t00 0.2090±0.0004 maineffectistohaltthestarformationofagalaxy,changingit Velocitydispersion[kms−1] 1320+64 fromstar-forming(SF)toquiescent.Otherpropertiesthatcould Virialradiusr [Mpc] 2.13±−06.705 200 beinfluencedbytheseprocessesare:stellarmass,size,andmor- phologicaltype.Thestudyofthedistributionoftheseproperties Notes.Theradiusr200correspondstotheradiusofaspherewhosemass andthecorrelationexistingamongthemandwiththeirenviron- overdensityis200timesthecriticaldensityattheclusterredshift.The mentgivesinformationabouttherelativeimportanceofthepro- valueoftheredshiftistakenfromMercurioetal.(2003a).Thevelocity cessesthataffecttheirevolution.Onepossiblewaytounderstand dispersioniscalculatedonourdataset(Sartorisetal.,inprep.),while thevirialradiusistakenfromMertenetal.(2015). the influence of these processes on the evolutionof galaxiesin clustersistosearchforeffectsoflocalenvironmentonthedistri- butionofgalaxystellar masses(M(cid:2)), i.e.thestellar massfunc- Anotherwaytoconstraintheeffectofdifferentenvironmen- tion(SMF),andcomparetheSMFofgalaxiesinclusterstothat tal processeson the evolutionof galaxiesis to analyzethe dis- inthefield. tribution of galaxy sizes and the relation with the stellar mass. To disentangle the effects of the environment on the SMF It is knownthat differenttypes of galaxies, namelyearly-types from the effects related to the morphology-density relation, (ETGs)andlate-typesshowdifferentdependenciesbetweensize i.e., the fact that the fraction of different morphological types andstellar mass (Shenet al. 2003).In particular,the mass-size changeswithlocaldensity(Dressler1980;Postmanetal.2005), relation of ETGs is steeper than the value found for late-type oneshouldstudytheSMFseparatelyfordifferenttypesofgalax- galaxies. How the environment may change the size distribu- ies.Sofar,thedeterminationoftheSMFhasbeenmainlybased tion of the galaxies is, instead, still a matter of debate. In the ondatainthefield(Ilbertetal.2013),whiletheevolutionwith local Universe, Poggianti et al. (2013) claim that at fixed stel- redshift (z) and the local environment of the SMF of different lar mass, cluster ETGs are slightly smaller than field galaxies. galaxytypesinclustershasnotyetbeenstudiedingreatdetail. On the other hand, Huertas-Companyet al. (2013) did not de- Onthe otherhand,the studyoftheluminosityfunction(LF)is tect any relation between galaxy sizes and environment.Many betterknown.Byseparatingthecontributionofearly-andlate- ofthephysicalprocessesthatcanaffectthepropertiesofcluster type galaxies using color indices, Popesso et al. (2006) show galaxiesarelikelytoberelatedtotheirorbits.Galaxiesonradial thatther-bandLFoflocallate-typegalaxiescanbefitted with orbits,characterizedbysmallpericenters,canexperiencedenser asingleSchechterfunction,whiletheLFofearly-typegalaxies environmentsthan galaxiesonmore tangentialorbits. Thiscan requires a double Schechter function. They also show that the leadtotheirmorerapiddestruction(Taylor&Babul2004).Ithas faint-endslopeoftheLFofearly-typegalaxiesexhibitsasignif- beensuggestedbySolanesetal.(2001)thatamongVirgocluster icant and continuousvariationwith the environment,flattening galaxies,thosewithevidenceofgasstrippingareonmoreradial in the central region of the cluster. They interpretthese results orbitsthantheothers. as an effect of galaxy transformationfrom star-formingto qui- In this paper, we investigate the SMF of passive and escent systems through harassment in the periphery and dwarf SF galaxies in the cluster Abell209 (hereafter A209) at tidaldisruptioninthecore. z= 0.209 as a function of the local environment and down to Vulcani et al. (2012, 2013) have found that global envi- amasslimitof108.6M(cid:3).Wealsoanalyzethedistributionofthe ronment does not affect the SMF of different galaxy types. sizesofpassiveearly-typegalaxiesindifferentmassrangesand Furthermore, they did not detect any difference between the in different cluster regions. Finally we determine the orbits for SMFsofthetotalpopulationofgalaxieswithinandoutsidethe clusterpassivegalaxiesintwomassbins. virialradiusofgalaxyclusters. Theseanalysesarebasedonanunprecedentedlargefraction However, it is also importantto note that the effects of the (>50%)of∼1000spectroscopicallyconfirmedclustermembers environmentcouldbeevidentonlybelowagivenmasslimitfor collectedattheESO-VLT,aspartoftheESOLargeProgramme agivenredshift.Forexample,atz∼1vanderBurgetal.(2013) 186.A-0798 (hereafter CLASH-VLT, P.I. Piero Rosati, Rosati findadifferenceinthe shapeoftheSMFofclustersandofthe et al. 2014). This is a spectroscopic follow-up of a subset of fieldbelow1010M(cid:3). 14southernclustersfromthe “ClusterLensingAndSupernova In Annunziatella et al. (2014), we studied the effect of en- surveywithHubble”(CLASH;seePostmanetal.2012). vironmentontheSMFofSFandpassivegalaxiesinthegalaxy The main propertiesof A209 are listed in Table1. We per- clusterMACS1206.2-0847(hereafterM1206)atthemeanred- formtheanalysisoftheSMFfortworeasons:tocheckwhether shiftofz= 0.44,byuseofalargefraction(∼1/3)ofspectroscop- theresultsfoundforthedynamicallyrelaxedclusterM1206also ically confirmedcluster members,downto M(cid:2)= 109.5M(cid:3). We holdforaclusterwithevidenceofsubstructures(Mercurioetal. havefoundthattheSMF ofbothgalaxytypesdoesnotchange 2003b)and,tostudypossibleredshiftevolutioneffectscompar- acrossthevirialradius1ofthatcluster.However,wediddetecta ingtheresultsobtainedinthetwoclusters,whichareseparated differenceontheSMFofpassivegalaxiesintheinnermostand by ∼2 Gyr in cosmic time. For A209, we also study the intra- densest region of the cluster in the form of a lack of galaxies cluster light(ICL) componentin order to get some hints about with M(cid:2)< 1010.5M(cid:3). Our hypothesis is that these galaxies in itsprogenitorsandtounderstandhowitisrelatedtotheevolution the very center of the cluster have been destroyed by tidal in- ofthegalaxiesinthecluster.Someoftheenvironmentaldepen- teractionswiththeclusterpotentialandhaveenrichedtheintra- dentmechanismthatshapetheSMFofclustermembergalaxies, clusterlight. infact,canalso beresponsiblefortheformationofthisdiffuse component.The ICL was first discoveredby Zwicky(1951)in 1 Thevirialradiusr istheradiusofaspherewithmassoverdensityΔ theComacluster.Itoriginatesfromtidalinteractionsamongthe 200 timesthecriticaldensityattheclusterredshift.Unlessotherwisestated, galaxies or with the cluster potential during the cluster assem- weadoptΔ=200throughoutthispaper. bly.Itisstillamatterofdebatewhichgalaxiescontributemore A160,page2of17 M.Annunziatellaetal.:A209stellarmassfunction totheICL.Fromatheoreticalpointofviewoneoftheproposed leading scenarios is that this componentcomes from tidal dis- ruptionofintermediatemassgalaxies(1010−11M(cid:3),Continietal. 2014). This scenario has also been supported by some obser- vationalworks(Annunziatellaetal. 2014;Presotto et al. 2015; DeMaio et al. 2015; Montes & Trujillo 2014). However, some authors (e.g. Conroy et al. 2007) suggest that the central ICL, associatedwiththeBCG,couldformfromdestructionofdwarf galaxies. The joint analysis of the ICL and the SMF of cluster memberscanshedsomelightonthistopic. The paper is organized as follows. In Sect. 2 we describe the data sample and explain how we assign the membershipto thegalaxiesinthefieldofview.InSect.3wederivethestellar massesof galaxiescluster members.InSect. 4 we estimate the SMFforclustermembersandexamineitsdependenceongalaxy typeandenvironment.InSect.5,wegiveabriefdescriptionof themethodusedtoderivethemapoftheintra-clusterlightand study some properties of the ICL in A209. In Sect. 6, we per- formtheanalysisoftheorbitsofpassivegalaxies.InSect.7we analyzethemass-sizerelationofpassivegalaxiesintworegions of the cluster. In Sect. 8 we show the stellar mass density and number density profiles compared with the total mass density profile obtained from an independentlensing analysis (Merten etal.2015).InSects.9and10wediscussourresultsanddraw Fig.1.HistogramoftheR -bandmagnitudeofthe51166objectsinthe C ourconclusions. photometric(blackline)sampleandofthe2622sourceswithreliable Throughout this paper, we use H = 70kms−1Mpc−1, redshifts(redline). 0 ΩM = 0.3, and ΩΛ = 0.7. At the cluster redshift the scale is 206kpcarcmin−1.Allthemagnitudesusedinthisworkreferto usingthe software SExtractor(Bertin & Arnouts1996)in con- theABsystem. junction with PSFEx (Bertin 2011; Annunziatella et al. 2013). By using a method based on neural networks (Brescia et al. 2013), we obtain the photometric redshift z for all galaxies 2. Datasample phot forwhichwehavethemagnitudesinalltheobservedbands.In Atotalof11LR-BluemaskswereacquiredwithVLT/VIMOS, this paper, we consider only galaxies down to the limit of the as part of the CLASH-VLT ESO large programme, using four observedspectroscopicsample:RC = 24.0mag(seeFig.1). separate pointings, each with a different quadrant centered on Todetermineifgalaxieswithz canbeclassifiedasmem- phot the cluster core. The LR-Blue masks cover the spectral range bers, we investigate the diagram shown in Fig. 2. We use the 370–670 nm with a resolving power R = 180, for a total ex- objectswithspectroscopicredshifttofindthebestselectioncri- posure time of 10.5 h. Spectra are classified according to the teria to identifycluster membergalaxies.Then,we applya cut reliability of the redshift (see Biviano et al. 2013)as: “secure” inthephotometricredshift.Weselectasclustermembersthose (QF = 3; 1946 objects) with a probability of >99.99%,“based galaxies with 0.175 < z < 0.272 (see horizontal lines in phot on emission-lines” (QF = 9; 110 objects) with a probabilityof Fig. 2). With these cuts in z we correctly classify 92% of phot ∼92%,and“likely”(QF=2;492objects)withaprobabilityof thespectroscopicmembers,minimizingthenumberofinterlop- ∼75%. ers. The sample of photometrically selected members contains Membership for objects with spectroscopic redshift is 1805 galaxies down to the magnitude limit of RC= 24.0 mag. assigned according to what is known as the “peak+gap” Theselectionofmembersbasedonphotometricredshiftsisnot (P+G) method (Fadda et al. 1996), already applied to M1206 asreliableasthatbasedonspectroscopicredshifts.Wetakethis (Bivianoetal.2013;Girardietal.2015).Thismethodidentifies intoaccountasexplainedinSect.2.1. apeakintheredshiftdistributionusinga1Dadaptivekernelal- gorithm,thenrejectsgalaxiesfromoverlappingradialbinsthat 2.1.Completenessandmembershipcorrections havelineofsightvelocitiesverydifferentfromthemeanvelocity ofthecluster. Oursampleneedstobecorrectedfortwodifferentfactors.One Thefinalspectroscopicdatasetconsistsof2548reliablered- is the incompleteness of the sample with photometric redshift shifts,observedaspartofCLASH-VLT,inadditionto110taken withrespecttothephotometricsample,sincetoobtainz ,we phot fromMercurioetal.(2003a)andMercurioetal.(2008).Intotal, requirethatthegalaxiesbedetectedinallfiveSUBARUbands. 1116areconfirmedmembers. Theothertakesintoaccountpossiblediscrepanciesbetweenz phot PhotometricdatawereobtainedwiththeSUBARU/Suprime- andz inthephotometricselectionofmembers,whichwecall spec Cam from SMOKA (Baba et al. 2002) covering a 30(cid:7) × 30(cid:7) membershipcorrection.Inordertoaccountforthesecorrections, fieldofview,withtotalexposuretimesof2400s,1800s,2400s, weapplythesamemethodasinAnnunziatellaetal.(2014). 1320s and 4800s in the B, V, R , I and z-band, respectively. The photometriccompleteness C is defined as the ratio be- c p Thetypicalseeinginthefinalsky-subtractedimagesvariesfrom tween the number of galaxies with photometric redshift and 0.486arcsecintheR-bandupto0.77intheB-bandwithapixel the total number of galaxies in the R -band. The complete- C scaleof0.2arcsec.Detailsonthedatareductioncanbefoundin nessC hasbeenevaluatedforthewholesampleandseparately Nonino et al. (2009). The photometric catalogs were extracted for red and blue galaxies, where we use the threshold value A160,page3of17 A&A585,A160(2016) 1.0 2.0 0.8 1.5 r o ct a f n 0.6 o1.0 cti e hot orr zp C 0.5 0.4 0.0 0.2 18.5 19.5 20.5 21.5 22.5 23.5 0.25 1.25 2.25 3.25 RC(mag) R(Mpc) Fig.3.Correctionfactor(f )formembershipselectionasafunctionof M R magnitude(leftpanel)andclustercentricdistance(rightpanel),for C 0.0 red(dots)andblue(diamonds)galaxies. 0.0 0.2 0.4 0.6 0.8 1.0 z spec Fig.2.Photometricvs.spectroscopicredshiftsforgalaxiesintheclus- 3. Measurementsofstellarmass terfieldandinthemagnituderange18 ≤R ≤ 24mag.Blackdotsare C spectroscopicallyconfirmedmembers.Thetwodashedlinesrepresent We use the spectral energy distribution (SED) fitting method thecriteriainphotometricredshiftschosentoclassifytheclustermem- to derive the stellar masses of the cluster members galaxies. bers.Galaxieswithinthisrangeofphotometricredshiftarecoloredin We make use of the code MAGPHYS (da Cunha et al. 2008). red.Galaxieswithz inthisrangeandwithoutspectroscopicinforma- For each galaxy, MAGPHYS finds the template at the redshift phot tionareclassifiedasmembers. Bluecrossesaregalaxiesoutsideboth of the galaxy that best reproduces the observed galaxy fluxes. thespectroscopicandphotometricselections. The templates are assembled from stellar population synthesis models (Bruzual & Charlot 2003 or Bruzual & Charlot 2007) withaChabrier(2003)stellarinitialmassfunctionandametal- licity value in the range 0.02–2 Z(cid:3). We adopt the Bruzual & Charlot (2003) library of models. The two libraries differ in the treatment of thermally pulsating asymptotic giant branch B−R = 1.5 (calculated on the basis of aperture magnitudes stellar phase which is not relevant at the mean redshift of the C within5(cid:7)(cid:7))todiscriminatebetweenthetwosamples.Thisvalue cluster A209 (Zibetti et al. 2013). In order to obtain the SED, forthecolorischosentomatchthelimitinspecificstarforma- MAGPHYS parametrizes the star formation history of a galaxy tionrate()usedtodistinguishbetweenPassiveandSFgalaxies withacontinuum,SFR∝e−γt,andsuperimposedrandombursts. (seeSect.3).TheparameterCisapproximatelyconstant,≥80%, The star formation timescale γ is distributed according to the downtoR ≤ 24magindependentlyfrommagnitudeorgalaxy probabilitydensityfunction p(γ)=1 − tanh(8γ − 6),whichis C type.Therefore,weadoptaconstantmeanvalueC=0.81anda uniform between 0 and 0.6 Gyr−1 and drops exponentially to correctionfactor,f =1/C=1.23. zero at 1 Gyr−1. The age of the galaxy is free to vary with an C upperlimitimposedbytheageoftheUniverseattheconsidered Toobtainthemembershipcorrectionfactor,weevaluatethe redshift. completenessandthepurityofthesampleofgalaxiesclassified Inordertofindthebest-fitmodel,MAGPHYSusesaBayesian as membersbased on their photometricredshift. We define the approach. As outputs, it produces the probability distribution completenessastheratiobetweenthenumberofgalaxiesiden- function of all the parameters and their best-fit values. For the tified as members(bothspectroscopicallyand photometrically) parameters we are interested in we adopt the median value as and the number of spectroscopic members CM=Npm∩zm/Nzm. themorerobustestimatewitha1σintervalgivenbythediffer- The purity is defined as the ratio between the number of ence between 16 and 84 percentilesof the probabilitydistribu- photometric members that are also confirmed spectroscopi- tion.Themeanvalueforthe1σuncertaintyonthestellarmass cally and the number of photometric members that have zspec, is∼0.07dex. P=Npm∩zm/Npm∩z. The membership correction factor is de- In Annunziatellaet al. (2014)we checkedthat the value of finedasf ≡P/C . InFig. 3we analyzethedependenceoff M M M thestellarmassisindependentofthespecificalgorithmofSED ongalaxytype,magnitude,anddistancefromtheclustercenter. fitting(providedoneconsidersthesamestellarIMF).However, Wefindthatthecorrectionfactordependsongalaxytype,while wefoundthatwhenonlyopticaldataisusedMAGPHYStendsto itisindependentofbothmagnitudeandclustercentricdistance. overestimatethe mass of a galaxybecausethe publicMAGPHYS Weusetwodifferentvaluesforredandbluegalaxiesintheentire librariescontainanexcessofstar-formingdustymodelswithre- magnitudeandradialrange,f =0.9and0.75,respectively. M spect to passive ones (E. da Cunha, priv. comm.). This means The finalcorrectionfactorwe appliedis givenbytheprod- that if the fluxes of a galaxy can be fitted by a dusty model or uct f · f (∼1.125 and 0.937 for passive and SF galaxies, by a truly passive one, the median value is always biased to- C M respectively). wards the dusty model. In order to avoid this systematic error A160,page4of17 M.Annunziatellaetal.:A209stellarmassfunction 2.2 12 2.0 11 1.8 1.6) ) g (cid:3) 10 a M m / 1.4( ∗ C M R g( 9 1.2− o L B 1.0 8 0.8 0.6 7 16 18 20 22 24 26 Fig.5. SMFsof SFand passive cluster member galaxies. The best-fit RC(mag) SchechterfunctionsareshownwiththebluedashedlineforSFgalax- iesandredtriple-dot-dashedlineforpassivegalaxies,whilethenum- Fig.4. Relation between the stellar mass and the R magnitude. The C ber counts(dividedbybinsize)arethebluesemicircleandredtrian- points are color-coded according to the B−R color. Dashed vertical C gle,respectively.Violetdiamondsarethecountsobtainedforallcluster andhorizontallinesarethemagnitudeandmasslimits,respectively. membersandthevioletsolidlinerepresentsthesumofthetwoSMFs. Counts are evaluated in bins of 0.2 dex in M(cid:2). The 1σ errors on the countshavebeenestimatedviathebootstrapresamplingprocedure. we made use of a non-public library of templates heavily biased tofit oldstellar populationswith verylittle star formation (provided by E. da Cunha). We proceed as follows. We per- free in these fits, while the normalization is fixed by imposing formedthe SED fitting for all the galaxiesin oursample using thattheintegraloftheSMFinthechosenmassrangebeequalto the standard libraries. Among its output parameters, MAGPHYS thetotalnumberofgalaxiesoftheconsideredsamplecorrected also provides an estimate of the specific star formation rate fortheweightfactor.Inthesefitseachgalaxyhasaweightequal (i.e., star formation rate per unit mass, sSFR ≡ SFR/M(cid:2)). We totheproductf ·f definedinSect.2.1.Wehavecheckedthat examined the values obtained for the sSFR and checked that C M thecontributionoftheerrorsonthestellarmassvalueissmaller this parameter has a bimodal distribution, with a local mini- thanthestatisticalerrorsassociatedwitheachoftheparameters mum at sSFR = 10−10 yr−1 (see also Lara-López et al. 2010, oftheSM.ThecorrectionfactorinFig.3,asshown,isindepen- and references therein). We then classified as passive galaxies dentfrommagnitudeorradialdistance.Therefore,theerrorson those with values of sSFR< 10−10 yr−1. Star-forming galax- this factor would influence only the normalizationof the SMF. ies, instead,havesSFR≥ 10−10 yr−1 Atthispointwe fitted the Theonlytwocasesinwhichwetookthenormalizationsintoac- passive galaxies again using the non-public library of models. countarewhenstudyingthetotalSMF(Sect.4.1)andwhenes- The limiting magnitude of RC= 24 mag corresponds roughly timatingthecontributionofgalaxiesofdifferentmasstotheICL to a completeness limit of 108.6M(cid:3) and to a surface bright- (Sect.5.2).Toestimatethecontributionoftheerrorsinthesetwo ness of 24.7 mag/arcsec2 for passive galaxies,accordingto the cases, we repeatedour calculationsusingf ±Δf . The results mass vs. R dispersion of Fig. 4 and to the measured galaxy M M C we obtained are statistically consistent with those obtained us- sizes (see Sect. 7). The mass limit for SF galaxies would be ing f . Thus, for ouranalysis we do notconsiderthe errorson lower. However, we chose the same value for passive galaxies M the membership correction factor. The cumulative SMF for all in order to be consistent when comparing the SMF of differ- galaxiesinA209isgiveninFig.5(violetline). entgalaxytypes.Withthismasslimit,ourfinalsampleconsists We are interested in studying how the SMF depends on of1916galaxies,morethanhalfofwhicharespectroscopically galaxytypeorenvironmentinordertoshedlightonthediffer- confirmedmembers. entprocessesthatcanaffecttheevolutionofgalaxiesinclusters. We wanted to compare only the shape of the SMF of different samples,sowerenormalizedtheSMFsbydividingthemforthe 4. Stellarmassfunction totalnumberofobjectsineachsample(exceptinFig.5).Inorder The SMF of cluster members is obtained by considering the toestablishiftwoSMFsarestatisticallydifferentwecompared number of galaxies in each stellar mass bin weighted for the the shape parameters (αandM∗) without taking the normaliza- completenessandthemembershipcorrectionfactors.Theerrors tionvaluesintoaccount.Tohighlightthedifferencebetweentwo onthecountsareestimatedwiththebootstrapprocedure(Efron SMFs, we also performedthe Kolmogorov-Smirnov(hereafter, &Tibshirani1986).TheSMFcanbeanalyticallydescribedbya K-S) test (e.g., Press et al. 1993). This is a non-parametrical Schechter(1976)function test that determines if two samples are drawn from the same (cid:2) (cid:3) (cid:2) (cid:3) parentpopulationbyevaluatingthemaximumdistancebetween Φ(logM)=ln(10)Φ∗ M 1+αexp −M d(logM), (1) their two cumulativedistributions. We used a modified version M∗ M∗ of the K-S test in order to include the weights on stellar mass (Annunziatellaetal.2014). whereαistheslopeofthelow-massend,M∗ istheexponential cutoff, and Φ∗ is the normalization. We fit the Schechter function to the M(cid:2) distribution downthe mass limit 108.6M(cid:3) using 4.1.Differentgalaxytypes the maximum likelihood technique (Malumuth & Kriss 1986). The separate SMFs of SF and passive cluster member galax- Theuseofthismethodimpliesthatonlytwoparametersareleft ies are shown in Fig. 5. The best-fit values of αandM∗ with A160,page5of17 A&A585,A160(2016) Table2.Best-fitSchechterfunctionparameters. Table 3. Best-fit Schechter function parameters for different environments. Galaxytype α log(M∗/M(cid:3)) Passive −1.09±0.02 11.10±0.05 Galaxytype Environment α log(M∗/M(cid:3)) SF −1.63±0.03 11.02±0.30 SF R>r200 −1.58±0.08 10.95±0.30 All −1.17±0.02 11.15±0.05 SF R≤r200 −1.69±0.07 11.42±0.45 Passive R>r −1.09±0.04 11.09±0.09 200 Passive R≤r −1.09±0.02 11.10±0.05 200 Passive Region(a) −1.01±0.06 11.21±0.12 Passive Region(b) −1.09±0.04 11.09±0.08 Passive Region(c) −1.10±0.03 11.09±0.08 Passive Region(d) −1.10±0.03 11.03±0.07 Table4.ResultsoftheK-Stests. Comparedsamples N1,N2 Prob.(%) Typedependence Passivevs.SFinthecluster 1580,336 <0.01 Passivevs.SFinRegion(b) 425, 34 <0.01 Passivevs.SFinRegion(c) 488, 75 <0.01 Passivevs.SFinRegion(d) 75,219 <0.01 Environmentdependence–SFgalaxies Fig.6.Best-fitvaluesoftheSchechterparametersαandM∗ withtheir 1σlikelihoodcontours. SFwithinandoutsider200 161,175 >10 SFinRegions(b)and(c) 34, 75 >10 SFinRegions(c)and(d) 75,219 >10 their 1σ errors are listed in Table 2 and shown in Fig. 6. The uncertaintiesareobtainedbymarginalizingoverthenormaliza- Environmentdependence–passivegalaxies tion parameter. The SMFs of, separately, SF and passive cluster members are adequately fitted by a single Schechter func- Passivewithinandoutsider200 438,408 >10 PassiveinRegions(a)and(b) 160,425 8 tion. In order to assess the goodness of the fits, we compared PassiveinRegions(b)and(c) 425,488 >10 themassdistributionofgalaxiesinthe consideredsample with PassiveinRegions(c)and(d) 488, 57 >10 thebest-fitSchechterfunctionusingtheK-Stest.Weperformed thistestforalltheSMFsconsideredinthispaper,exceptforthe Notes.ThevaluesN1andN2arethenumberofgalaxiesineachofthe SMFofallclustermembers,alwaysobtaining P-values>10%. comparedsubsamples.Theprobabilitiesinthelastcolumnsarereferred Therefore,wecannotrejectthenullhypothesisthatthetwodis- tothenullhypothesisthatthestellarmassdistributionsofthetwosam- tributions are statistically identical. The SMF of passive and plesaredrawnfromthesameparentpopulation. Avalue≤1%means SF cluster members is given by the sum of the SMFs of sep- that the two distributions are statistically different. Samples with less arately SF and passive galaxies. The dependence of the SMF that10objectsareexcludedfromthetest. on galaxy type is statistically significant. This is evident from the comparison of the shape of the two SMFs and also from theresultsoftheK-Stest(seeTable4).Thedifferencebetween passivegalaxiesinthetwoclustersatdifferentredshiftsisqual- themassdistributionofpassiveandSFgalaxiesholdsnotonly itatively in agreementwith the results shown in Rudnick et al. when considering the whole cluster, but also in different clus- (2009).Intheirpaper,theauthorsfoundthattheluminosityfunc- ter regions. From Fig. 5 we see that the passive SMF domi- tionsofpassivegalaxiesshowedastrongevolutionwithredshift nates over the SF SMF at all masses down to the complete- in terms of an increase of faint galaxies relative to bright ones ness limit in A209. In Annunziatella et al. (2014), we found towards lower redshifts. Another feature of the passive galaxy that the two SMFs of SF and passive galaxies for the cluster SMFisthedipvisibleinthegalaxycountsat∼1010.10M(cid:3).The M1206 at z ∼ 0.44 crossed at the value Mcross ∼ 1010.1M(cid:3), if presence of this dip was also found in the luminosity function wifewceornessitdreicreteddththeewahnoalleyscilsuisntesridreegthioenv,iarniadlMregcrioossn∼of1th0e9.5cMlu(cid:3)s-, oatftrheed-mseaqguneintucedegainlaxthieesRof-btahnisdc∼lu9s.t8erm(aMg,erwcuhriciohectoarlr.e2sp0o0n3dbs) ter.Thedifferencebetweenwhathappensinthetwoclusterscan (according to the fit in Eq. (3)) to our mass value. This dip is bepartiallyexplainedbytheButcher−Oemlereffect(Butcher& probablys an indication that there are two populations of pas- Oemler1978),accordingtowhichgalaxyclustersatintermedi- sivegalaxies,oneoflowermassesprobablyoriginatingfromthe ateredshiftcontainalargerfractionofbluegalaxiesthanlower quenchingofSFgalaxies,andanotherofhighermasses.Tover- redshift ones. On the other hand, there is a striking difference ifythiswefitadoubleSchectertoourdatainSect.4.3. betweentheslopeoftheSMFofpassivegalaxiesthatwefindin thisworkandthevaluewefoundforpassivegalaxiesinM1206 4.2.Effectsofglobalandlocalenvironments (α = −0.38 ± 0.06).Wecheckedthatthisdifference passiveM1206 in slope is not due to the differentcompleteness limits that we To investigate the environmental dependences of the SMF, we reach in the two works. The difference between the SMF of considered SF and passive galaxies separately. In this way we A160,page6of17 M.Annunziatellaetal.:A209stellarmassfunction 12.0 10 10.5 ) −2 min) 5 1.800 1.800 9.0 min c Y(arcBCG 0 9.000 4.500 67..05 ensity(ar − 4.5 d −5 el Y 3.0 ern K −10 RTH 1.5 O EASTN 15 10 5 0 -5 -10 -15 X − XBCG(arcmin) Fig.9.Spatialdistributionofclustermembersdowntothestellarmass limit. The points are colored according to the local number density. Coordinates refer to the position of the BCG (black star). Red, light Fig.7.SMFsofSF(left)andpassive(right)galaxiesinsideandoutside greenandbluelinesidentifygalaxiesbelongingtoRegions(a),(b)and the virial radius of the cluster. The SMFs are normalized to the total (c)definedinthetext.PointsoutsidethecontoursbelongtoRegion(d). numberofgalaxiesineachsample. Thebluestarrepresentsthepositionofthehighestdensitypeak. differentregionsaccordingtotheirnumberdensity(intermsof galaxiesperarcmin−2): (a) Σ> 9.0; (b) 4.5< Σ ≤ 9.0; (c) 1.8< Σ ≤ 4.5; (d) Σ ≤ 1.8. It can be seen in Fig. 9 that regions identified by Σ are not spherically symmetric. Another peculiar characteristic is that Region(a)isnotcenteredontheBCGandthatRegions(b)and (c) also incorporate a group in the N-NE direction. Mercurio et al. (2003a) found that the center of the cluster was coinci- dentwiththepositionoftheBCG.However,theyusedasample ofbrighterspectroscopicallyconfirmedmembergalaxies.Their magnitude limit (R < 22 mag) roughly corresponds to a mass Fig.8.AsinFig.6:best-fitSchechterparametersM∗ andαwiththeir limit>109.5M(cid:3) (seeFig.4).Ifwelimitouranalysistothissam- ple of galaxiesthe center is coincidentwith the position of the 1σcontourindifferentregionsofthecluster BCG andtheregionathighdensityin theNWdirectiondisap- pears;inotherwords,themorphologicalappearanceoftheclus- terchangesaccordingtothelimitingmagnitudeofthesample. areabletoexcludetheeffectsofthedependenceofgalaxypop- The group in the N-NE direction contains very few cluster ulationfromenvironment(Dressler1980). spectroscopicmembers.Forthisreason,weremoveditfromour First,weconsideredtheSMFsofSFandpassivegalaxiesin- analysis after checkingafter we checkedthat its presence does sidethevirialradiusofthecluster(r200)andoutside(∼1.7r200). notaffecttheSMFofgalaxiesindifferentregions. TheSMFsandtheirbest-fitSchechterparametersareshownin Figure10showstheSMFofpassivegalaxiesinRegions(a) Figs. 7 and 8. The SMFs of SF galaxiesinside and outside the to(d),andtheirbest-fitparametersarereportedinFig.11andin virialradiusarestatisticallyindistinguishable(seetheresultsof Table3.Figures10and11showthattheSMFofpassivegalaxies theK-StestinTable4).Thesameresultholdsforpassivegalax- dependsonthelocaldensity.Theenvironmenthastwoeffectson iesaswell. theSMFofpassivegalaxiesinthedensestregionofthecluster: We define the “environment” in units of the local density thereisahighernumberofhigh-massgalaxiesthaninlessdense (numberofgalaxiesperarcmin−2).Wedecidedtousethisdefini- regions(whichcorrespondstoahighervalueofM∗)butthereis tionofenvironmentinsteadoftheradialdistancefromtheBCG alsoadropatthelowendoftheSMF. (Annunziatellaetal.2014)sinceA209isanelongated,dynami- We applied the K-S test separately to the M(cid:2) distributions callynotfullyrelaxedcluster(Fig.9)andtheregionsidentified ofSFandpassivegalaxiesinadjacentregions.Accordingtothe bylocaldensityareelongatedwithrespecttothoseidentifiedby resultsoftheK-Stest,inRegions(a)to(d)theM(cid:2)distributions clustercentricradius. of both SF and passive galaxies are not statistically different. Thelocaldensityisobtainedwithakerneldensityfunction, However,this can be related to the fact that low-mass galaxies wheretheprojecteddistributionofthegalaxiesissmoothedwith statisticallydominatethesamples.Ifwerepeatthetestrestrict- a Gaussian kernel in an iterative way. Figure 9 shows the dis- ing it to the galaxies with M(cid:2)>109.5M(cid:3), we find a significant tribution of galaxies in the cluster. The points are color-coded difference between the mass distribution of passive galaxies in according to the value of the local density (Σ). We define four Regions(a)and(b). A160,page7of17 A&A585,A160(2016) Fig.10. SMFs of passive galaxies in different density regions. The Fig.12. SMFs of passive cluster member galaxies within and outside SMFsare normalized tothetotal number of galaxies ineach sample. r200. The red solid and orange dashed lines are the best-fit double Redcircles,orangetriangles,maroonsquares,andmagentadiamonds Schechterfunctions.Thepointsandtherelativeerrorbarshavethesame arenumbercountsinRegion(a)to(d). meaningasinFig.7(rightpanel) . Fig.11.AsinFig.6:best-fitSchechterparametersM∗andαwiththeir 1σcontourindifferentdensityregionsofthecluster. Fig.13.SMFsofpassiveclustermembergalaxiesinRegions(a)to(d). Thelinesarethebest-fitdoubleSchechterfunctions.Thepointsandthe relativeerrorbarshavethesamemeaningasinFig.10. 4.3.DoubleSchecter EvenifthesingleSchechterisstatisticallyanacceptablefittoall (Mortlocketal. 2015;Baldryetal. 2012).In Fig.12,we show theSMFspresentedinthispaper,thedipexistinginthenumber the double Schechter fit to the SMF of passive galaxies within countsofpassivegalaxiesinallenvironmentsandtheupturnin and outside the virialradiusof the cluster, while in Fig. 13 we thenumbercountsatthelow-massendvisibleinthelowdensity showthedoubleSchechterfitinRegions(a)to(d).Thebest-fit regionsseem to indicate that perhapsa doubleSchechterfunc- valuesoftheparametersarelistedinTable5.BothFig.13and tion is more suitable to describe the SMF of this galaxy pop- Table 5 show thatin the densest regionof the cluster the slope ulation. For this reason we fit a double Schechter function to ofthetwoSchechterfunctionsarestatisticallyindistinguishable, theSMFofpassivegalaxiesinalltheenvironments.Thedouble meaningthatadoubleSchechterfunctiondoesnotprovideabet- Schechterfunctionusedhasfourfreeparameters: terfitthanasingleone.Theevidenceoftwopopulationsofpas- Φ(logM)=ln(10)Φ∗ sive galaxies becomes stronger when movingto outer and less ⎡(cid:7) (cid:8) (cid:7) (cid:8) ⎤ (cid:7) (cid:8) denseregionsofthe cluster.Thisisalso shownbytheincrease ×⎢⎢⎢⎢⎢⎣ M 1+α+f M 1+α2⎥⎥⎥⎥⎥⎦×exp − M d(logM). (2) ofthedifferencebetweenthetwoslopesoftheSchechterfunc- M∗ 2 M∗ M∗ tions.ThesecondcomponentintheSMFofpassivegalaxiesis hypothesizedinthemodelofPengetal.(2010b),asaresultof Compared to the single Schechter function there are two addi- the environmental quenching of SF galaxies. The fact that we tional free parameters: the slope of the second component α , observeasecondcomponentthatisstrongerintheouterregions 2 and the ratio between the normalizationsof the two functions, couldmeanthattheenvironmentalprocessesresponsibleforthe f =Φ∗/Φ∗. We considerthe same M∗ forthe two functionsto quenchingaremosteffectiveintheexternalregionsoftheclus- 2 2 minimize the number of free parameters and to follow the ap- teror thatin thecenterthesemechanismsarestrongenoughto proach already used for the study of the SMF of field galaxies completelydestroythispopulationofgalaxies. A160,page8of17 M.Annunziatellaetal.:A209stellarmassfunction Table5.Best-fitparametersofthedoubleSchechterfunctionofpassivegalaxiesinallenvironments. Environment α log(M∗/M(cid:3)) f2 α2 Passive −0.61±0.25 10.96±0.08 0.76±0.25 −1.18±0.23 r ≤ r −0.93±0.27 11.08±0.07 0.76±0.33 −1.18±0.28 200 r > r −0.05±0.34 10.77±0.10 0.44±0.25 −1.21±0.10 200 Region(a) −1.01±0.14 11.21±0.12 0.65±0.41 −1.01±0.22 Region(b) −0.94±0.08 11.06±0.10 0.34±0.35 −1.24±0.26 Region(c) −0.41±0.35 10.93±0.10 0.81±0.32 −1.19±0.09 Region(d) −0.34±0.36 10.70±0.11 0.10±0.23 −1.48±0.29 )(cid:3) 11.3 strippedbythesegalaxiescouldcontributetotheICL.Tocheck M 11.2 SingleSchechter ifthishypothesisholdsinthisclusteraswellweneedtoobtain / ∗M 11.1 anICLmapandanestimateoftheICLcolorandmass. g( 11.0 Intra-clusterlightisadiffusecomponentthatoriginatesfrom o l starsboundtotheclusterpotential;thesestarsaretidallystripped −1.10 from the outer regions of galaxies that interact with the BCG −1.05 α or other cluster members (Murante et al. 2007; Contini et al. −1.00 −0.95 SingleSchechter 2014). Some properties of the ICL, such as the radial profile, thecolor,andpresenceofsubstructurearestrictlylinkedtothe ) 11.4 (cid:3) accretionhistoryanddynamicalevolutionofgalaxyclusters.For M 11.2 / 11.0 example,thepresenceoftidal arcscangiveinformationonthe ∗ M 10.8 assemblyhistoryofthe cluster.If theICL is formedbeforethe g( 10.6 DoubleSchechter cluster has undergonevirialization,the bulk of the ICL will be o l smoothwithfewfainttidalarcs.Accordingtotheoreticalmodels −1.0 −0.8 thesefeaturesaretheresultofrecentinteractionamonggalaxies α1 −−00..64 with the cluster potential (Rudick et al. 2009). The color can −0.2 DoubleSchechter alsogivesomehintsonwhicharethemainprogenitorgalaxies 0.0 oftheICL.EveniftheICLcanshedlightonmanymechanisms −1.7 occurringingalaxyclusters,isverydifficulttostudyitowingto −1.5 2 −1.3 DoubleSchechter itsveryfaintsurfacebrightness,i.e.,∼1%oftheskybrightness. α −1.1 Furthermore, the detection of the ICL at high redshift is made −0.9 even more difficult by the surface brightness dimming, which scaleswithredshiftas(1 + z)4. 0.65 R ToobtaintheICLmapwefollowedthemethoddevelopedby N0.55 GS0.45 Presottoet al. (2015).Inthe followingsections, we summarize themainaspectsofthismethod. 0.35 0 2 4 6 8 10 12 Σ(numberofgalaxies/arcmin2) 5.1.ICLdetectionmethod Fig.14.Fromtoptobottom:best-fitparametersofthesingleSchechter There is no consensus on the method for the detection of the (panels1and2)andofthedoubleSchechterfunctions(panels3−5)for ICL.Ideally,oneshouldsubtractthelightcontributionfromall passive galaxies and the GSNR (panel 6) as a function of the cluster galaxiesintheclusterincludingtheBCG.However,itisnotal- localnumberdensity.Regions(d)to(a)fromlefttoright. wayspossibletoperfectlyfitthelightdistributionofeachgalaxy. For this reason, in many works the galaxies are masked down In Fig. 14, we show the parameters of the SMF of passive to a certainlimitin surfacebrightness.The approachwe use is galaxiesasafunctionofthelocaldensityofthecluster.Wealso a hybridmethod which first fits a Sérsic profile to each galaxy showtheratiobetweenthenumberofgiantandsubgiantgalax- andsubtractsthebest-fitmodelwheneverpossible,thenitmasks ies(GSNR)asafunctionoftheenvironment.Wedividethegi- all the pixels with high residuals. We use this method to ana- ant and subgiant galaxies using a mass threshold of 1010.0M(cid:3), lyze the RC image of the cluster. Since the region affected by i.e. the mass value at which the SMFs of passive galaxies in the ICL is ∼500kpcaround the BCG, we limit our analysis to Region(a)and(b)intersect.ThetrendintheGSNRshowsthat a squaredimage ∼1 Mpc in size centeredon the BCG. We use in Region (a) the ratio between the number of giant and sub- an automated procedure that relies on the GALAPAGOS soft- giantgalaxiesishigherthaninlessdenseregions.Thistrendis ware (Barden et al. 2012). The main goal of GALAPAGOS is consistentwiththeonewefoundinM1206. to obtain a Sérsic fit for all the sources detected in the image bySExtractor(Bertin& Arnouts1996).Thefits are performed bytheGALFITcode(Pengetal.2010a).Detailedexplanations 5. Intra-clusterlight of how GALAPAGOS works is given in Barden et al. (2012). In Annunziatella et al. (2014) we found that the SMF of pas- Here,we brieflydescribeonlythestepsthatare crucialforour sive galaxies in the innermost and densest region of the clus- analysis. terM1206declinesatthelow-massend.Wesuggestedthatthis The detection of the sources is performedby SExtractor in steeper drop could be explained by the tidal stripping of sub- two-stepruns:onecalled“cold”,whichistunedtoproperlyde- giant galaxies (M(cid:2) < 1010.5M(cid:3)). In our scenario, the material tectanddeblendonlybrightsources,andtheothercalled“hot”, A160,page9of17 A&A585,A160(2016) whichisfocusedonthedetectionoffaintones.Thetwodetec- Table6.Best-fitparametersofthethreecomponentsoftheSérsicfitof tions are then combined by rejecting the faint sources that are theBCG+ICL. located inside the cold source as determined by the Kron el- lipse (Kron 1980). The input parameters are chosen to detect Component R n mag e tot in the hotmode sourceswith S/N > 1σ . For each detected (h−1kpc) (ABmag) sky 70 source, GALAPAGOS creates a stamp image large enough to 1(BCG) 0.86 0.5 20.07 include neighbor galaxies and centered on the source posi- 2(BCG) 44.28 3.07 16.15 tion. Then,GALFIT simultaneouslyfits all the sourcesin each 3(ICL) 120 1.51 16.57 stamp. The starting parameters for the fits are the SExtractor estimate of source position (X_IMAGE, Y_IMAGE), the source total magnitude (MAG_BEST), its effective radius (function of We used the magnitude value obtained from the fit to esti- matetheICLmass.Weperformabi-weightedfitoftherelation FLUX_RADIUS),anditspositionangle(THETA_IMAGE).The between the stellar masses of red cluster member galaxies that outputparametersfromthefitsandthoseobtainedbySExtractor are in the subsample image analyzed with GALAPAGOS and arethencombinedinafinalcatalog.ThenweusetheGALtoICL theirtotalR magnitudeprovidedbyGALFIT: procedure presented in Presotto et al. (2015). This procedure C merges the stamps created by GALAPAGOS to form a global log(M/M(cid:3)) = (18.41±0.07)−(0.41±0.02)×RCtotmag. (3) modelimage which is later subtracted from the originalimage to obtain a residual image called BCG+ICL map. The sources Using this relation with the total RC magnitudes obtained from the multicomponent Sérsic fit, we estimate thathavehighresidualsareidentifiedbycomparingthedistribu- tion of the residualswith the distributionofthe pixelvaluesof MICL = (2.9±0.7)× 1011M(cid:3) and MBCG = (6.2 ± 1.2) × askyregion.Thepixelswhosevaluesdeviateatdifferentσlev- 1011M(cid:3). The mass of the BCG obtained in this way is con- els from the sky (1, 2, 3, 4, 5σ ) are flagged and associated sistent with the mass obtained when applying MAGPHYS, i.e. tothecorrespondingsource.Thesskeypixelscanbemaskedorone 6.2±1.2 × 1011M(cid:3). To check if the ICL can form from tidal stripping of sub- thesourcescanbemanuallyre-fitthetothecorrectlevel.Before the BCG+ICL map is created one can also decide to manually giants galaxies (i.e. galaxies with M(cid:2) <1010.0M(cid:3)), we have to evaluatethemissingmassfromsubgiantgalaxiesinRegion(a). addmasks(forexampleincaseofstellarspikes). Themissingmassfromsubgiantgalaxiesisdeterminedwiththe InFig.15,weshowtheR imageofA209(firstpanel),the C globalmodelimage(secondpanel)andtheBCG+ICLmapwith equation pixelsat1σsky level(thirdpanel).Wecancheckifthesubtrac- (cid:12) 1010.0M(cid:3) (cid:12) 1010.0M(cid:3) tionofthelightfromthesourceswasdoneinanefficientwayby ΔM ≡ MΦ∗(M)dM− MΦ (M)dM, (4) sub a a countingthe percentageof maskedpixels. In ourcase thisper- 108.6M(cid:3) 108.6M(cid:3) centagevariesfrom7%to10%ifwemaskat5σskyor1σsky. whereΦa istheSMFofpassivegalaxiesinRegion(a)notnor- malized, while Φ∗ is the SMF of passive galaxiesif we substi- a tute the value of the slope with the best-fit value obtained for 5.2.ICLproperties the SMF in Region(b). The integralis donebetween the com- We estimate the B − R color of the BCG+ICL map. To do pletenessmasslimitandthemassatwhichtheSMFsofpassive C this we take as a benchmarkthe global model in the RC-band. galaxiesinRegions(a)and(b)intersecteachother(∼1010.0M(cid:3)). From this we obtain a model for the B-band by changing the The upper and lower error on ΔM are estimated by sub zeropointand fitting only the magnitudesof the objects. Then, repeating the evaluation of Eq. (4) and fixing the slope to wgeetstuhbetrBa-cbtatnhdisBmCoGde+lIfCrLommtahpe.BA-tbathnidsipmoaingte,owfethdeegclruasdteerthtoe αof±ΔMδα. TihsefvoarlmuealloyfiΔnMasgubreiesm1e.n4t−+00w..75ith×M1011Mw(cid:3)i.thTinhe1vσa.luAe sub ICL BCG+ICL map in the R -band to the PSF of the B-band by similar agreement between ΔM and M was also found C sub ICL convolving it with a Gaussian function whose σ is the differ- in M1206. Breaking the integral in Eq. (4) we can estimate encebetweenthetwoPSFsandfromthiswesubtracttheB-band the contribution to ΔM coming from galaxies in different sub BCG+ICLmap.TheB−R coloroftheBCG+ICLis∼2.1mag mass ranges: the main contribution is given by galaxies in the C at the position of the BCG while it drops to 1.2 mag at a dis- massrange109.5 < M(cid:2) <1010.0M(cid:3)(60%),galaxiesinthemass tancefromtheBCG of∼110kpc.Inthisradialrange,thecolor range109.0 < M(cid:2) <109.5M(cid:3) contribute∼30%,while galaxies oftheBCG+ICLremainsinthecolorrangeofthepassivecluster in the range 108.6 < M(cid:2) <109.0M(cid:3) only 10%. This suggests members(seeFig.4). thattheICLcouldoriginatefromthestrippingofstarsfromsub- ThesurfacebrightnessprofileofBCG+ICLdeviatesfroma giant galaxies in the mass range 109.0 < M(cid:2) <1010.0M(cid:3). On singleSérsicprofile(Presottoetal.2015).Forthisreasonwefit the contrary,this result seems to rule outthat the disruptionof theBCG+ICLlightprofilewithasumofmultiplecomponents. dwarf galaxies is the main channel for the formation of ICL, Moustakasetal.(inprep.)modelthesurfacebrightnessprofileof which agrees with the predictions from semi-analytical mod- theBCGsofeachCLASHcluster.Theyfindthatthelightprofile els (Contini et al. 2014). Our result is also consistent with re- oftheBCGofA209,contrarytotheotherBCGsinthesample, centfindingsfromobservationalworks.Indetail,DeMaioetal. deviates from a single Sérsic profile. They perform the fits in (2015),useasubsampleofCLASHclustersat0.44 ≤ z ≤ 0.57 all HST bandpasses and assume a universal value of nandR . todeterminethecolorgradientsandtotalluminosityoftheICL. e We chose to fit the BCG+ICL profile with three components: Their main conclusionis that the ICL originatesfrom the tidal twocomponentsfortheBCGswiththeeffectiveradius(R )and destruction of 0.2 L* galaxies (which corresponds to galaxies e the Sérsic index fixed to the values found in Moustakas et al., of ∼1010.0 M(cid:3)). In a completely independent way, Longobardi and another one for the ICL. The best-fit parameters for the etal.(2015)assessthatthePlanetaryNebulaeintheintra-cluster three components are listed in Table 6. The position angles of mediumoftheVirgoclustercanbeassociatedwithagalaxypro- thethreecomponentsareconsistentwithintheuncertanties.The genitorthatisfourtimesthemassoftheLargeMagellanicCloud reducedχ2ofthefitis1.535. (∼109.5M(cid:3)). A160,page10of17

Environment-driven evolution of galaxies in the z = 0.209 cluster Abell 209

Similar Environment-driven evolution of galaxies in the z = 0.209 cluster Abell 209