2004AJ....127..798S

We present the results of a search for clusters in dwarf irregular galaxies in the Virgo and Fornax Clusters using Hubble Space Telescope (HST) WFPC2 snapshot data. The galaxy sample includes 28 galaxies, 11 of which are confirmed members of the Virgo and Fornax Clusters. In the 11 confirmed members, we detect 237 cluster candidates and determine their V magnitudes, V-I colors, and core radii. After statistical subtraction of background galaxies and foreground stars, most of the cluster candidates have V-I colors of -0.2 and 1.4, V magnitudes lying between 20 and 25 mag, and core radii between 0 and 6 pc. Using Hα observations, we find that 26% of the blue cluster candidates are most likely H II regions. The rest of the cluster candidates are most likely massive (>10⁴ M_☉) young and old clusters. A comparison between the red cluster candidates in our sample and the Milky Way globular clusters shows that they have similar luminosity distributions but that the red cluster candidates typically have larger core radii. Assuming that the red cluster candidates are in fact globular clusters, we derive specific frequencies (S_N) ranging from ∼0 to 9 for the galaxies. Although the values are uncertain, seven of the galaxies appear to have specific frequencies greater than 2. These values are more typical of elliptical and nucleated dwarf elliptical galaxies than they are of spiral or Local Group dwarf irregular galaxies.