A catalog of globular cluster systems: What determines the size of a galaxy's globular cluster population?

Abstract

We present a catalog of 422 galaxies with published measurements of their globular cluster (GC) populations. Of these, 248 are E galaxies, 93 are S0 galaxies, and 81 are spirals or irregulars. Among various correlations of the total number of GCs with other global galaxy properties, we find that N GC correlates well though nonlinearly with the dynamical mass of the galaxy bulge , where σe is the central velocity dispersion and Re the effective radius of the galaxy light profile. We also present updated versions of the GC specific frequency SN and specific mass S M versus host galaxy luminosity and baryonic mass. These graphs exhibit the previously known U-shape: highest SN or SM values occur for either dwarfs or supergiants, but in the midrange of galaxy size (109-1010 L ·) the GC numbers fall along a well-defined baseline value of SN ≃ 1 or SM = 0.1, similar among all galaxy types. Along with other recent discussions, we suggest that this trend may represent the effects of feedback, which systematically inhibited early star formation at either very low or very high galaxy mass, but which had its minimum effect for intermediate masses. Our results strongly reinforce recent proposals that GC formation efficiency appears to be most nearly proportional to the galaxy halo mass Mhalo. The mean "absolute" efficiency ratio for GC formation that we derive from the catalog data is M GCS/M halo = 6 × 10-5. We suggest that the galaxy-to-galaxy scatter around this mean value may arise in part because of differences in the relative timing of GC formation versus field-star formation. Finally, we find that an excellent empirical predictor of total GC population for galaxies of all luminosities is NGC (Re σe )1.3, a result consistent with fundamental plane scaling relations. © 2013. The American Astronomical Society. All rights reserved.