The Subaru FMOS Galaxy Redshift Survey (FastSound). III. The massa€“metallicity relation and the fundamental metallicity relation at za€‰a??a€‰1.4

摘要

Wepresenttheresultsfromalargenear-infraredspectroscopicsurveymadewithSubaru/FMOS(FastSound)consistingofa??a€‰4000galaxiesatza€‰a??a€‰1.4withsignificantH?±detection.Wemeasurethegas-phasemetallicityfromthe[Na€‰ii]??6583/H?±emissionlineratioofthecompositespectrainvariousstellarmassandstar-formationratebins.Theresultingmassa€“metallicityrelationgenerallyagreeswithpreviousstudiesobtainedinasimilarredshiftrangetothatofoursample.Nocleardependenceofthemassa€“metallicityrelationonstar-formationrateisfound.Ourresultatza€‰a??a€‰1.4isroughlyinagreementwiththefundamentalmetallicityrelationatza€‰a??a€‰0.1withafiberaperturecorrectedstar-formationrate.Wedetectsignificant[Sa€‰ii]????6716,6731emissionlinesfromthecompositespectra.Theelectrondensityestimatedfromthe[Sa€‰ii]????6716,6731lineratiorangesfrom10a€“500??cma?’3,whichgenerallyagreeswiththatoflocalgalaxies.Ontheotherhand,thedistributionofoursampleon[Na€‰ii]??6583/H?±vs.[Sa€‰ii]????6716,6731/H?±isdifferenttothatfoundlocally.Weestimatethenitrogen-to-oxygenabundanceratio(N/O)fromtheN2S2index,andfindthattheN/Oingalaxiesatza€‰a??a€‰1.4issignificantlyhigherthanthelocalvaluesatafixedmetallicityandstellarmass.Themetallicityatza€‰a??a€‰1.4recalculatedwiththisN/Oenhancementtakenintoaccountdecreasesby0.1a€“0.2??dex.Theresultingmetallicityislowerthanthelocalfundamentalmetallicityrelation.