Direct Evidence for Dynamical Evolution of Luminosity Functions of Globular Cluster Systems: HST/ACS observations of the 3-Gyr-old merger remnant NGC 1316

Abstract

Recent observations of globular clusters (GCs) in intermediate-age (2-4 Gyr old), early-type merger remnants have provided the hitherto `missing link' between young merger remnants and `normal' elliptical galaxies in the form of a GC subsystem with colors and luminosities consistent with population synthesis model predictions for those ages and ~solar metallicity. Here we present new, deep observations of the GC system of the intermediate-age merger remnant NGC 1316, using the ACS camera aboard Hubble Space Telescope, which allowed us to create luminosity functions (LFs) as a function of galactocentric radius. We find that the inner 50% of the `red' GC system shows a clear turnover in its LF, at about 1 mag fainter than that of the `old' blue GCs. This constitutes direct, dynamical evidence that metal-rich GC populations formed during a gas-rich merger can evolve into the `red', metal-rich GC populations that are ubiquitous in `normal' giant ellipticals.

4 pages, to be published in "The Formation and Evolution of Massive Young Star Clusters", edited by H.J.G.L.M. Lamers, A. Nota & L.J. Smith (ASP: San Francisco)