Newly Identified Star Clusters in M33. I. Integrated Photometry and Color-Magnitude Diagrams

We present integrated photometry and color-magnitude diagrams (CMDs) for 24 star clusters in M33, of which 12 were previously uncataloged. These results are based on Advanced Camera for Surveys observations from the Hubble Space Telescope of two fields in M33. Our integrated V magnitudes and V-I colors for the previously identified objects are in good agreement with previously published photometry. We are able to estimate ages for 21 of these clusters using features in the CMDs, including isochrone fitting to the main-sequence turnoffs for 17 of the clusters. Comparisons of these ages with the clusters' integrated colors and magnitudes suggest that simple stellar population models perform reasonably well in predicting these properties.

Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with proposal GO-9873 (principal investigator: A. Sarajedini).