Galactic Stellar and Substellar Initial Mass Function

作者：Gilles Chabrier · 发表于：Publications of the Astronomical Society of the Pacific · 年份：2003 · DOI：10.1086/376392 · 被引用次数：9121 · 研究领域：Astrophysics and Star Formation Studies、Astronomy and Astrophysical Research、Stellar, planetary, and galactic studies

We review recent determinations of the present-day mass function (PDMF) and initial mass function (IMF) in various components of the Galaxy-disk, spheroid, young, and globular clusters-and in conditions characteristic of early star formation.As a general feature, the IMF is found to depend weakly on the environment and to be well described by a power-law form for M , and a lognormal form below, except possibly for m տ 1 early star formation conditions.The disk IMF for single objects has a characteristic mass around M , m ∼ 0.08 c and a variance in logarithmic mass , whereas the IMF for multiple systems has M , and .The extension of the single MF into the brown dwarf regime is in good agreement with present estimates of Land T-dwarf densities and yields a disk brown dwarf number density comparable to the stellar one, n ∼ n ∼ BD * pc Ϫ3 .The IMF of young clusters is found to be consistent with the disk field IMF, providing the same correction 0.1 for unresolved binaries, confirming the fact that young star clusters and disk field stars represent the same stellar population.Dynamical effects, yielding depletion of the lowest mass objects, are found to become consequential for ages տ130 Myr.The spheroid IMF relies on much less robust grounds.The large metallicity spread in the local subdwarf photometric sample, in particular, remains puzzling.Recent observations suggest that there is a continuous kinematic shear between the thick-disk population, present in local samples, and the...