Abstract

Recent studies of early type galaxies suggest that the initial stellar mass function (IMF) varies with galaxy property (such as [Fe/H]). Globular clusters (GCs) formed at similar redshifts and in similar environments as galactic bulges, and are important places to test the non-universal IMF hypothesis. The variation of the mass-to-light ratios (M/L) of GCs in the Milky Way and M31 with [Fe/H] are larger than what is predicted by stellar population models, and this has been attributed to IMF variations. In this talk I show that the observed variations are due to biases as the result of mass segregation and the data can be explained by a single (I)MF. We present comparisons of new multi-component models to data of several Milky Way GCs and show that the low-mass end of the (I)MF can not be constrained from integrated properties. The data are more sensitive to the high-mass end of the MF and this can be used to put indirect constraints on the high-mass end of the IMF via the stellar remnants and the initial-final mass relation. Finally, the presence of a stellar-mass black hole population leaves distinct imprints in the phase-space density of the visible stars and a possible detection of this signal in a Milky Way GC is presented.