New insights from Hubble Space Telescope studies of globular cluster systems. II. Analysis of 29 S0 systems

We examine the globular cluster systems (GCSs) of a sample of 34 S0 galaxie s from a WFPC2 snapshot survey in the V and I bands. Of these 34 galaxies, 29 have measurable globular cluster systems. The mean color of the GCSs of individual galaxies vary from V-I = 0.85 mag to V-I = 1.17 mag. The average color of GCSs in all 29 S0 galaxies, V-I = 1.00 +/- 0.07 mag, is similar t o the value of V-I = 1.04 +/- 0.04 derived for ellipticals in a companion p aper. The mean metallicity of a cluster system is correlated to the luminos ity (or mass) of the host galaxy, but it is not dependent on the Hubble typ e. Our measurements of the local specific frequency, on the other hand, con firm that the cluster formation efficiency is a function of Hubble type. Th e mean local specific frequency of our sample within the WFPC2 field of vie w is 1.0 +/- 0.6, lower than S-N(Local) = 2.4 +/- 1.8 derived for elliptica ls in a similar analysis. Although we are able to confirm a bimodal color d istribution in only one galaxy from the shallow "snapshot" images analyzed in this paper, statistical tests suggest that 10%-20% of S0s are bimodal at the present level of photometric accuracy. There are no significant trends in GCS properties with membership or location of the S0 host in a galaxy c luster. We have measured the turnover luminosity of the globular cluster lu minosity function (GCLF) for the richest few GCSs and find the GCLF distanc es to be in agreement with other estimates. The globular clusters in S0 gal axies have average half-light radii of approximate to2.6 pc, which is simil ar to that of other galaxies, including our own.