Institute of Astronomy

The mass function of stars and black holes in globular clusters

SpeakerTalk DateTalk Series
Mark Gieles (University of Surrey)3 March 2016Institute of Astronomy Colloquia


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.


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