Clustering Properties of Low-Luminosity Star-Formi

arXiv:0808.1337v1[astro-ph]9Aug2008ClusteringPropertiesofLow-LuminosityStar-Forminggalaxiesatz=0.24and0.40intheSubaruDeepField∗AkiNakajima,1YasuhiroShioya,2TohruNagao,1,2TomokiSaito,2TakashiMurayama,3ShunjiS.Sasaki,1,3AsukaYokouchi,[e-mail]1GraduateSchoolofScienceandEngineering,EhimeUniversity,Bunkyo-cho,Matsuyama790-85772ResearchCenterforSpaceandCosmicEvolution,EhimeUniversity,Bunkyo-cho,Matsuyama790-85773AstronomicalInstitute,GraduateSchoolofScience,TohokuUniversity,Aramaki,Aoba,Sendai980-8578(Received00;accepted00)AbstractWepresentouranalysisontheclusteringpropertiesofstar-forminggalaxiesse-lectedbynarrow-bandexcessesintheSubaruDeepField.SpecificallywefocusonHαemittinggalaxiesatz=0.24andz=0.40inthesamefield,toinvestigatepossibleevolutionarysignaturesofclusteringpropertiesofstar-forminggalaxies.Basedontheanalysison228Hαemittinggalaxieswith39.8logL(Hα)40.8atz=0.40,wefindthattheirtwo-pointcorrelationfunctionisestimatedasξ=(r/1.62+0.64−0.50Mpc)−1.84±0.08.ThisissimilartothatofHαemittinggalaxiesinthesameHαluminosityrangeatz=0.24,ξ=(r/1.88+0.60−0.49Mpc)−1.89±0.07.ThesecorrelationlengthsaresmallerthanthoseforthebrightergalaxysamplestudiedbyMeneuxetal.(2006)inthesameredshiftrange.Theevolutionofcorrelationlengthbetweenz=0.24andz=0.40isinterpretedbythegravitationalgrowthofthedarkmatterhalos.Keywords:galaxies:distancesandredshifts—galaxies:evolution—cosmology:large-scalestructureofuniverse1.INTRODUCTIONFormationandevolutionofgalaxiesanditsdependenceontheenvironment,e.g.,thefor-mationoflarge-scalestructure,arefundamentalproblemsofthemoderncosmology.Studyingtheevolutionoftheclusteringofgalaxiesisusefultounderstandtheevolutionofgalaxiesand*BasedondatacollectedatSubaruTelescope,whichisoperatedbytheNationalAstronomicalObservatoryofJapan.1thatoflarge-scalestructures.Galaxiesareconsideredtoformwithindarkmatterhalos.OwingtotheWMAPobservations(Spergeletal.2007),thecosmologicalparametersarewelldeter-minedandtheevolutionoftheclusteringofdarkmatterhalosisnowwellunderstoodbothanalytically(Mo&White1996;Sheth&Tormen1999)andfromN-bodysimulations(Jenkinsetal.1998;Kauffmannetal.1999;Springeletal.2005).However,physicalrelationshipbetweengalaxypopulationsandthedarkmatterhalosisnotclear,sincegalaxyformationprocessesincludegascooling,starformation,andfeedback.Atthepresentuniverse,galaxiesselectedfromopticalobservationsareconsideredtotracethedistributionofunderlyingdarkmatterhalos(Verdeetal.2002).However,thestrengthoftheclusteringdependsonpropertiesofgalaxypopulations:e.g.,luminosity(Zehavietal.2005),colororspectraltype(Zehavietal.2002),andstellarmass(Lietal.2006).Thedependenceofclusteringonthepropertiesofgalaxiesgivesconstraintontheoriesofgalaxyfor-mation.Toconstrainthemodelofgalaxyformation,itisusefultoinvestigatesuchdependencesindetail.Inthispaper,weconcentratethedependenceofclusteringontheluminosityofgalax-ies.Norbergetal.(2001)fittherelativebiasb/b∗asafunctionofL/L∗,b/b∗=0.85+0.15L/L∗,whereb∗isthebiasforL∗galaxiesandthebiasisdefinedasthesquarerootoftheratioofthegalaxyanddarkmattercorrelationfunctions,b≡(ξg/ξDM)1/2.UsingtheSDSSdata,Tegmarketal.(2004)gaveanotherfittingfunction,b/b∗=0.85+0.15L/L∗−0.04(M−M∗).Therelativebiasatthelow-luminosityendissmallerthantheTegmark’srelationinZehavietal.(2005).Thereforetherelativebiasoflow-luminositygalaxiesisstillcontroversial.Recently,thedependenceofclusteringontheluminosityisstudieduptoz∼1.5fromtheVIMOS-VLTDeepSurvey(Marinonietal.2005;Meneuxetal.2006;Polloetal.2006),theDEEP2GalaxyRedshiftSurvey(Coiletal.2006),andtheCanada-FranceLegacySurvey(CFHTLS,McCrackenetal.2008).Brightergalaxiesaremorestronglyclusteredthanlowluminositygalaxiesandthedependenceofrelativebiasontheluminosityatz∼0.8isinagreementwiththatinthelocalUniverse(Marinonietal.2005).Theobserveddecreasingoftheclusteringstrengthisconsistentwithsimplegravitationalgrowthpicture(Meneuxetal.2006).However,theevolutionoftheclusteringoflow-luminositygalaxiesisnotcleartillnow,sincethoseobjectsaretoofaintforspectroscopicsurveys.Inthispaper,wepresenttheclusteringpropertiesofHαemittersatz=0.24andz=0.40,whicharelow-luminosityactivestar-forminggalaxiesintheSubaruDeepField.TheirmeanabsolutemagnitudeishMBi∼−17.0,whichis1magfainterthanthepreviousobservations(Polloetal.2006;Meneuxetal.2006).Wethereforestudytheevolutionofgalaxieswithlowluminosities.Usingthenarrowbandimagingsurvey,weselectstar-forminggalaxieswithintherestrictedredshifttofaintermagnitudes.Throughoutthispaper,magnitudesaregivenintheABsystem.WeadoptaflatuniversewithΩmatter=0.3,ΩΛ=0.7,andH0=70kms−1Mpc−1.22.PHOTOMETRICCATALOGInthispaper,weusetheofficialphotometriccatalogsoftheSubaruDeepField(SDF)projectthatisaverydeepopticalimagingsurveyusingtheSuprime-Cam(Miyazakietal.2002)onthe8.2mSubaruTelescope(Kaifuetal.2000;Iyeetal.2004)atMaunaKeaObservatories.TheSDFislocatedneartheNorthGalacticPole,centeredatα(J2000)=13h24m38s.9andδ(J2000)=+27◦29′25′′.9.DetailsoftheSDFprojectaregiveninKashikawaetal.(2004).TheSDFofficialphotometriccatalogsareobtainedfromtheSDFwebsite(ht