The Globular Cluster Luminosity Functions of Brightest Cluster Galaxies

A new technique for studying globular cluster populations around relatively distant galaxies is developed and applied to a sample of 23 galaxies in 19 Abell clusters. The technique is based on the surface brightness fluctuations method of determining galaxy distances. The galaxies in this sample range in redshift from 5000 to 10,000 km s1, and were selected from the Lauer & Postman (1994) survey. The analysis assumes that the mean magnitude of the globular cluster luminosity functions (GCLFs) in galaxies near the centers of rich clusters does not vary significantly; this assumption is scrutinized before proceeding with the Abell cluster study. The zero point of the GCLF mean is set with respect to Virgo, and is therefore independent of the Hubble parameter. The specific frequency Sn of globular clusters within a metric radius of 32 h1 Mpc is found to correlate strongly with the velocity dispersion of the galaxies in the cluster, the cluster X-ray temperature and luminosity (especially "local" X-ray luminosity), and with the number of bright neighboring galaxies. SN correlates less strongly with galaxy profile, and only marginally with galaxy luminosity and overall cluster richness. It does not correlate with cluster morphology class. Within a cluster, galaxies at smaller projected distances from the X-ray center have higher values of SN. Together with the relative constancy of BCG luminosity, these results suggest a scenario in which globular clusters form in proportionate numbers to the available mass, but central galaxy luminosity "saturates" at a maximum threshold, resulting in higher SN values for central galaxies in denser clusters. As a byproduct of the analysis, the Gaussian width ac of the GCLF is measured. In the cosmic microwave background frame, the mean GCLF width for this sample is (a) = 1.43 mag, virtually identical to the M87 HST value. This provides a self-consistency check on the assumption of a constant GCLF mean magnitude. Thesis Supervisor: John L. Tonry Title: Professor of Physics