We show that the globular cluster mass function (GCMF) in the Milky Way depends on cluster half-mass density, ρh, in the sense that the turnover mass M_(TO) increases with ρ_h, while the width of the GCMF decreases. We argue that this is the expected signature of the slow erosion of a mass function that initially rose toward low masses, predominantly through cluster evaporation driven by internal two-body relaxation. We find excellent agreement between the observed GCMF-including its dependence on internal density ρ_h, central concentration c, and Galactocentric distance r_(gc)-and a simple model in which the relaxation-driven mass-loss rates of clusters are approximated by -dM/dt = μ_(ev) ∝ ρ_h~(1/2)· In particular, we recover the well-known insensitivity of M_(TO) to r_(gc). This feature does not derive from a literal "universality" of the GCMF turnover mass, but rather from a significant variation of M_(TO) with ρ_h,-the expected outcome of relaxation-driven cluster disruption-plus significant scatter in ρ_h, as a function of r_(gc). Our conclusions are the same if the evaporation rates are assumed to depend instead on the mean volume or surface densities of clusters inside their tidal radii, as μ_(ev) ∝ ρ_t~(1/2) or μ_(ev) ∝ ∑_t~(3/4) - alternative prescriptions that are physically motivated but involve cluster properties (p_t and ∑_t) that are not as well defined or as readily observable as ρ_h,. In all cases the normalization of μ_(ev) required to fit the GCMF implies cluster lifetimes that are within the range of standard values (although falling toward the low end of this range). Our analysis does not depend on any assumptions or information about velocity anisotropy in the globular cluster system.
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