|Affiliation||University of Kiel|
|Accepted by||Monthly Notices of the Royal Astronomical Society|
Determinations of the power-law indices "alpha" are subject to systematic errors arising mostly from unresolved binaries. The systematic bias is quantified here, with the result that the single-star IMFs for young star-clusters are systematically steeper by "Delta" "alpha" ~ 0.5 between 0.1 and 1 MO than the Galactic-field IMF, which is populated by, on average, about 5 Gyr old stars. The MFs in globular clusters appear to be, on average, systematically flatter than the Galactic-field IMF (Piotto & Zoccali 1999; Paresce & De Marchi 2000), and the recent detection of ancient white-dwarf candidates in the Galactic halo and absence of associated low-mass stars (Méndez & Minniti 2000; Ibata et al. 2000) suggests a radically different IMF for this ancient population. Star-formation in higher-metallicity environments thus appears to produce relatively more low-mass stars. While still tentative, this is an interesting trend, being consistent with a systematic variation of the IMF as expected from theoretical arguments.