On the Evolution of the Globular Cluster Luminosity Function: The Differences

Abstract

We consider the observational signature of the dynamical effects on the luminosity function of globular clusters. For the three best studied systems, in Milky Way, M31, and M87, there is a statistically significant difference between the inner and outer population of globular clusters. In all cases the inner clusters are on average brighter than the outer clusters ($0.26 < \Delta m_0 < 0.84$) and have a smaller dispersion in magnitudes ($0.04 < \Delta \sigma < 0.53$), with the larger differences for the local, better observed samples. The differences are of the type that would be expected if the inner population had been depleted by tidal shocks. The results suggest that the inner population suffers substantial evolution from its initial distribution and cannot not be used as a standard candle without correction for dynamical evolution.