Program: GS-2006A-Q-24

From a recent HST/ACS imaging survey of several Brightest Cluster Galaxies (BCGs), we have found a striking new systematic feature of their large globular cluster systems. Although the GCs in these galaxies all clearly display the now-classic "bimodal" metallicity distribution, the blue (metal-poor) clusters by themselves become progressively more metal-rich with increasing luminosity. By contrast, giant E galaxies that do NOT happen to be BCGs do not seem to exhibit this same trend. This new correlation may suggest that BCGs were built from systematically more massive progenitor clouds than other large galaxies, within which partial self-enrichment could occur during the earliest, metal-poor round of GC formation. If this interpretation is valid, then it favors the idea that BCGs are basically different from other types of gE's right from the start. We propose to image 6 southern BCGs with GMOS to test this new phenomenon (and our interpretation) further.