Young Clusters in the Nuclear Starburst of M83

Abstract

We present a photometric catalog of 45 massive star clusters in the nuclear starburst of M83 (NGC 5236), observed with the Hubble Space Telescope Wide Field Planetary Camera 2, in both broadband (F300W, F547M, and F814W) and narrowband (F656N and F487N) filters. By comparing the photometry with theoretical population synthesis models, we estimate the age and mass of each cluster. We find that over 75% of the star clusters more massive than 2×10⁴ M_solar in the central 300 pc of M83 are less than 10 Myr old. Among the clusters younger than 10 Myr and more massive than 5×10³ M_solar, 70% are between 5 and 7 Myr old. We list an additional 330 objects that are detected in our F300W images but not in the shallower F547M and F814W images. The clusters are distributed throughout a semicircular annulus that identifies the active region in the galaxy core, between 50 and 130 pc from the optical center of M83. Clusters younger than 5 Myr are preferentially found along the northwestern end of the semicircular annulus, and the northwest region also corresponds to the highest equivalent widths of the Hα emission [EW(Hα)] values. The cluster ages are consistent with a burst of star formation that began <~10 Myr ago. However, the current data cannot exclude a longer duration of activity, because the star clusters may dissolve on a ~10 Myr timescale. We discuss both possible scenarios. Based on observations made 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 NAS 5-26555.