Constraints on the Global Mass-to-Light Ratios and Extent of Dark Matter Halos in Globular Clusters and Dwarf Spheroidals

Abstract

The detection of stars in the process of being tidally removed from globular clusters and dwarf spheroidals in the Galaxy's halo provides a strong constraint on their mass to light ratios and on the extent of their possible dark matter halos. If a significant dark matter component existed either within or beyond the observed stellar distribution, then stars would not be removed. We use numerical simulations to study mass loss from two component star clusters orbiting within a deeper potential. We find a global upper limit on the mass to light ratios of globular clusters, M/L \lsim 2.5, and rule out the possibility that they have extended halos of low luminosity material. Similarly, the tidal tails of dwarf spheroidals indicates that their dark matter halos must be truncated at \sim 400 pc therefore they have total mass to light ratios \lsim 100.