VANSEVICIUS V., KODAIRA K., NARBUTIS D., STONKUTE R., BRIDZIUS A., DEVEIKIS V. and SEMIONOV D.
Abstract (from CDS):
We have carried out a survey of compact star clusters (apparent size ≲3'') in the southwest part of the M31 galaxy, based on the high-resolution Suprime-Cam images (17'.5x28'.5), covering ∼15% of the deprojected galaxy disk area. The UBVRI photometry of 285 cluster candidates (V ≲ 20.5 mag) was performed using frames of the Local Group Galaxies Survey. The final sample, containing 238 high probability star cluster candidates (typical half-light radius rh∼ 1.5 pc), was selected by specifying a lower limit of rh≳ 0".15 (≳0.6 pc). We derived cluster parameters based on the photometric data and multiband images by employing simple stellar population models. The clusters have a wide range of ages from ∼5 Myr (young objects associated with 24 µm and/or Hα emission) to ∼10 Gyr (globular cluster candidates), and possess mass in a range of 3.0 ≲ log(m/m☉) ≲ 4.3 peaking at m ∼ 4000 m☉. Typical age of these intermediate-mass clusters is in the range of 30 Myr ≲ t ≲ 3 Gyr, with a prominent peak at ∼70 Myr. These findings suggest a rich intermediate-mass star cluster population in M31, which appears to be scarce in the Milky Way galaxy.