NEWLY IDENTIFIED STAR CLUSTERS IN M33. II. RADIALHUBBLE SPACE TELESCOPE/ADVANCED CAMERA FOR SURVEYS FIELDS

We present integrated photometry and color–magnitude diagrams (CMDs) for 161 star clusters in M33, of which 115 were previously uncataloged, using the Advanced Camera For Surveys Wide Field Channel onboard the Hubble Space Telescope . The integrated V -band magnitudes of these clusters range from M V ∼–9 to as faint as M V ∼–4, extending the depth of the existing M33 cluster catalogs by ∼1 mag. Comparisons of theoretical isochrones to the CMDs using the Padova models yield ages for 148 of these star clusters. The ages range from log( t ) ∼ 7.0 to log( t ) ∼ 9.0. Our CMDs are not sensitive to clusters older than ∼1 Gyr. We find that the variation of the clusters' integrated colors and absolute magnitudes with age is consistent with the predictions of simple stellar population models. These same models suggest that the masses of the clusters in our sample range from 5 × 10 3 to 5 × 10 4 M ☉ .