Growth of Velocity Dispersions for Collapsing Spherical Stellar Systems
[摘要] First,wehaveensuredthatsphericalnonrotatingcollisionlesssystemscollapsewhilealmostretainingtheirsphericalconfigurationsduringtheinitialcontractionphases,eveniftheyareallowedtocollapsethree-dimensionally.Next,basedontheassumptionofsphericalsymmetry,weexaminetheevolutionofthevelocitydispersionswithcollapseforthosesystemshavinguniformorpower-lawdensityprofileswithMaxwellianvelocitydistributionsbydirectlyintegratingthecollisionlessBoltzmannequation.Theresultsshowthatasfarastheinitialcontractionphasesareconcerned,theradialvelocitydispersionnevergrowsfasterthanthetangentialvelocitydispersion,exceptatsmallradii,wherethenearlyisothermalnatureremains,irrespectiveofthedensityprofilesandvirialratios.Thisimpliesthatthevelocityanisotropyasaninitialconditionshouldbeapoorindicatoroftheradialorbitinstability.Thegrowingbehaviorofthevelocitydispersionsisbrieflydiscussedfromtheviewpointthatphase-spacedensityisconservedincollisionlesssystems.
[发布日期] [发布机构]
[效力级别] [学科分类] 天文学(综合)
[关键词] "Galaxies: formation";"Galaxies: structure";Instabilities;"Methods: numerical";"Stellar dynamics" [时效性]
