Detection Rate of Molecular Gas in Elliptical Galaxies: Constraints on Galaxy-Formation Theories

[摘要] Wecalculatedthedetectionrateofcoldgasinellipticalgalaxiesusingasemi-analyticmodelofgalaxyformation,andcompareditwithobservations.Wehaveshownthatamodelwithalongstar-formationtime-scale(∼20Gyr)isinconsistentwithobservations.Thus,somemechanismsofreducingthemassofinterstellarmedium,suchastheconsumptionofmoleculargasbystarformationand/orreheatingfromsupernovae,arecertainlyeffectiveingalaxies.Ourmodelpredictsthatstarformationisinducedwhengalaxiesinahalocollidewitheachotheranditreducesthecoldgasleftuntilthepresent.However,wefindthatthereductionthroughrandomcollisionsofsatellite(non-central)galaxiesinthemean-freetime-scaleinahaloisnotrequiredtoexplaintheobservations.ForcDgalaxies,thepredicteddetectionrateofcoldgasisconsistentwithobservationsaslongasthetransformationofhotgasintocoldgasispreventedinhaloswhosecircularvelocitiesarelargerthan500;km;s−1.Moreover,wefindthatthecoldgasbroughtintocDsthroughcapturinggas-richgalaxiesissmall.Wealsoshowthatthefractionofgalaxieswithobservablecoldgasshouldbesmallforclusterellipticalsincomparisonwiththatforfieldellipticals.Ourfiducialmodelsandthemodelswithalargereheatingefficiencycanreproducetheobservationswell,althoughacomparisonwithalargerandcompletesampleofellipticalgalaxieswillconstrainthephysicalparametersingalaxy-formationtheoriesmorestrictly.

[学科分类] 天文学(综合)

[关键词] "galaxies: clusters: general";"galaxies: clusters: intracluster medium";"galaxies: elliptical and lenticular;cD";"galaxies: ISM"