Evolution of the Luminosity-Metallicity-Stellar Mass correlation in a hierarchical scenario
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arXiv:astro-ph/0603059v1 2 Mar 2006EvolutionoftheLuminosity-Metallicity-StellarMasscorrelationinahierarchicalscenario
Mar´ıaEmiliaDeRossi1,2,PatriciaBeatrizTissera1,2andCeciliaScannapieco1,2
1ConsejoNacionaldeInvestigacionesCient´ıficasyT´ecnicas,Argentina
2InstitutodeAstronom´ıayF´ısicadelEspacio,CiudaddeBuenosAires,
Argentinaderossi@iafe.uba.ar
Summary.WestudytheevolutionoftheStellarMass-MetallicityRelationandtheLuminosity-MetallicityRelationbyperformingnumericalsimulationsinacos-mologicalframework.WefindthattheslopeandthezeropointoftheLuminosity-MetallicityRelationevolveinsuchawaythat,atagivenmetallicity,systemswere∼3magbrighteratz=3comparedtogalaxiesinthelocaluniverse,whichiscon-sistentwiththeobservationaltrend.ThelocalStellarMass-MetallicityRelationshowsalsoagoodagreementwithrecentobservations.WeidentifyacharacteristicstellarmassMc∼1010.2M⊙h−1atwhichtheslopeoftheMMRdecreasesforlargerstellarmasses.OurresultsindicatethatMcarisesnaturallyasaconsequenceofthehierarchicalbuildingupofthestructure.
1ResultsanddiscussionTheLuminosity-MetallicityRelation(LMR)hasbeenwidelystudieddur-ingthelasttwodecades.Inthelocaluniversethereisaclearcorrelationbetweentheluminosityandthechemicalabundanceofgalaxiesinsuchawaythatbrightersystemstendtobemoremetalrich(e.g.[3]).Futhermore,recentobservationshavesuggestedthatthiscorrelationevolveswithred-shift(e.g.[2]).Atagivenluminositysystemsseemtobelessenrichedinthepast.Becauseofthedifficultiesinobtainingstellarmass,moststudieshaveusedgalaxyluminosityasasurrogate.Recently,though,therelationbetweenoxygenchemicalabundanceandstellarmass(MMR)hasbeenestimatedforlocalgalaxiesfindingawelldefinedcorrelation[6].InthisworkwestudytheMMRandtheLMRbyusingchemo-dynamicalsimulationsinacosmologicalscenario,whichallowustofollowthenon-linealgrowthofstructuretogetherwiththechemicalenrichmentoftheinterestellarmedium.Wehaveperformedchemo-dynamicalsimulationsbyemployingthechem-icalGADGET-2[4].AΛCDMuniverse(Ω=0.3,Λ=0.7,Ωb=0.04andH0=100h−1kms−1Mpc−1,h=0.7)wasassumed.Thesimulatedvolumecorrespondstoaperiodiccubicboxofacomoving10Mpch−1sidelength.Wehaveconsideredtworunsinitiallyresolvedwith2×1603and2×803particles(fordetailsseeDeRossietal.2006inpreparation).OursimulationspredictalocalLMRwhichisingoodagreementwiththeobservationalfindings(e.g.[2]amongothers).Theslopeandthezero2Mar´ıaEmiliaDeRossi,PatriciaBeatrizTisseraandCeciliaScannapiecopointoftheLMRevolvewithtimeinsuchawaythatsystems,atagivenchemicalabundance,are∼3magbrighteratz=3comparedwithlocalones.Themajorvariationsinchemicalabundancearedrivenbythefaintestsystems.WehavealsoanalysedtheMMRobtainingsimilartrendstothoseencounteredby[6]forSDSSgalaxiesbutwithadisplacementof∼−0.25dexinthezeropoint.ThisdiscrepancymaybeduetothefactthattheSDSSexploresonlythecentralregionsofgalaxiesleadingtoanoverestimationofthemetalcontentofthesystems.WealsoobserveanexcessofmetalsatlowermassesforthesimulatedMMRwhichmaybeprobablyassociatedtothelackofstrongenergyfeedbackinournumericalmodel.Themetallicityofgalacticsystemstendstoincreasewithstellarmassinanon-linearway.WehavedeterminedacharacteristicmassMc∼1010.2M⊙h−1
wheretheslopeoftheMMRdecreasesandtherelationstartstoflattenforlargermasses[5].Itisimportanttonotethatthismassisindependentofredshiftandhasbeenpreviouslymentionedintheliteratureasacharac-teristicmassforgalaxyevolution[1].Byexaminingthehistoryofevolutionofeachindividualgalacticsystem,wefoundthatthosewithstellarmassesM∗>Mchaveexperiencedimportantmergereventsathighredshiftcausinganaccelerationinthetransformationofgasintostars.Atlowerredshiftsthesesystemsaresaturatedofstarsandhence,whiletheirstellarmasssignificantlyincreasesduringamergerevent,theirmetallicityremainsalmostthesame.Ontheotherhandlessmassivesystemsformtheirstarsinamorepassivewayorbyrichgasmergersleadingtoamoretightcorrelationbetweenstellarmassandmetallicity.Thus,thepatternsoftheMMRarecloselyrelatedtothehierarchicalaggregationofstructureinaLCDMuniverseandhenceitmightbeconsideredafossilofthisprocess.MEDRthankstheLOCofthisconferencefortheirfinancialsupport.ThisworkhasbeenpartiallysupportedbyCONICET,Fundaci´onAntorchasandLENAC.
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