GLOBULAR CLUSTER POPULATIONS: RESULTS INCLUDING S⁴G LATE-TYPE GALAXIES

Using 3.6 and 4.5 μm images of 73 late-type, edge-on galaxies from the S⁴G survey, we compare the richness of the globular cluster populations of these galaxies to those of early-type galaxies that we measured previously. In general, the galaxies presented here fill in the distribution for galaxies with lower stellar mass, M_∗, specifically log(M_∗/M_⊙, overlap the results for early-type galaxies of similar masses, and, by doing so, strengthen the case for a dependence of the number of globular clusters per 10⁹M_⊙ of galaxy stellar mass, T_N, on M_∗. For 8.5 < log(M_∗/M_⊙ < 10.5 we find the relationship can be satisfactorily described as T_N=(M_∗/10^6.7)^-0.56 when M_∗ is expressed in solar masses. The functional form of the relationship is only weakly constrained, and extrapolation outside this range is not advised. Our late-type galaxies, in contrast to our early types, do not show the tendency for low-mass galaxies to split into two T_N families. Using these results and a galaxy stellar mass function from the literature, we calculate that, in a volume-limited, local universe sample, clusters are most likely to be found around fairly massive galaxies (M_∗ ∼ 10^10.8M_⊙) and present a fitting function for the volume number density of clusters as a function of parent-galaxy stellar mass. We find no correlation between T_N and large-scale environment, but we do find a tendency for galaxies of fixed M_∗ to have larger T_N if they have converted a larger proportion of their baryons into stars.