IAU Symposium Abstract S186-078P


Keck Spectroscopy of Protoglobular Clusters in the Merger Galaxies NGC 1275, NGC 6052 and Arp 222.

Jean P. Brodie
Lick Observatory, University of California, Santa Cruz, USA (brodie@ucolick.org)

We present the results of a spectroscopic study with the Keck telescope of protoglobular cluster candidates in three galaxies, NGC 1275, NGC 6052 and Arp 222, each of which displays clear evidence of merger activity in the recent past. We measure the equivalent widths of age and metallicity/luminosity-sensitive spectral features. We derive radial velocities for the clusters and estimate their ages using stellar evolutionary models and by comparing their spectra with stellar and cluster templates covering a range of spectral types and ages. The NGC 1275 system is the best-studied and most complex of these merger galaxies. Its protoglobulars are very young but there is evidence that their IMFs are skewed to high-masses. This may be evidence against their formation in the cooling flow but also casts doubts on their eventual evolution to normal globular clusters. We compare the cluster motions with the local flow of the emitting gas and with the velocity structure of the underlying galaxy. We discuss the implications of our results for current ideas of cluster formation in merging systems.