The Dependence of Globular Cluster Number on Density for Abell Cluster Central Galaxies

A study of the globular cluster systems of 23 brightest, or central, galaxiesin 19 Abell clusters has recently been completed. This Letter presents some ofthe newly discovered correlations of the globular cluster specific frequency$S_N$ in these galaxies with other galaxy and cluster properties and puts forthan interpretation of these results. $S_N$ is found to correlate strongly withmeasures of the cluster density, such as the velocity dispersion of the clustergalaxies and the cluster X-ray temperature and luminosity (especially ``local''X-ray luminosity). Within a cluster, galaxies at smaller projected distancesfrom the X-ray center are found to have higher values of $S_N$. Taken together,the scaling of $S_N$ with cluster density and the relative constancy of centralgalaxy luminosity suggest a scenario in which globular clusters form inproportionate numbers to the available mass, but galaxy luminosity``saturates'' at a maximum threshold, resulting in higher \sn\ values forcentral galaxies in denser clusters as well as the suitability of thesegalaxies as ``standard candles.'' Thus, these galaxies do not have too manyglobular clusters for their luminosity; rather, they are underluminous fortheir number of globular clusters.Comment: 10 pages, with 4 included postscript figures; AASTeX (aaspp4.sty); to appear in ApJ Letter