Star clusters in M33: updated UBVRI photometry, ages, metallicities, and masses

Abstract

The photometric characterization of M33 star clusters is far from complete. In this paper, we present homogeneous $UBVRI$ photometry of 708 star clusters and cluster candidates in M33 based on archival images from the Local Group Galaxies Survey, which covers 0.8 deg${}^2$ along the galaxy's major axis. Our photometry includes 387, 563, 616, 580, and 478 objects in the $UBVRI$ bands, respectively, of which 276, 405, 430, 457, and 363 do not have previously published $UBVRI$ photometry. Our photometry is consistent with previous measurements (where available) in all filters. We adopted Sloan Digital Sky Survey $ugriz$ photometry for complementary purposes, as well as Two Micron All-Sky Survey near-infrared $JHK$ photometry where available. We fitted the spectral-energy distributions of 671 star clusters and candidates to derive their ages, metallicities, and masses based on the updated {\sc parsec} simple stellar populations synthesis models. The results of our ${\chi }^2$ minimization routines show that only 205 of the 671 clusters ($31\%$) are older than 2 Gyr, which represents a much smaller fraction of the cluster population than that in M31 ($56\%$), suggesting that M33 is dominated by young star clusters ($<1$ Gyr). We investigate the mass distributions of the star clusters---both open and globular clusters---in M33, M31, the Milky Way, and the Large Magellanic Cloud. Their mean values are $\log (M_{\mathrm{cl}}/M_{\odot })=4.25$, 5.43, 2.72, and 4.18, respectively. The fraction of open to globular clusters is highest in the Milky Way and lowest in M31. Our comparisons of the cluster ages, masses, and metallicities show that our results are basically in agreement with previous studies (where objects in common are available); differences can be traced back to differences in the models adopted, the fitting methods used, and stochastic sampling effects.

32 pages, 12 figures, 2 tables, accepted for publication in ApJS

References in corpus (11)

• A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33
• Radial variation of attenuation and star formation in the largest late-type disks observed with GALEX
• Globular Cluster Systems in Giant Ellipticals: the Mass/Metallicity Relation
• RR Lyrae Variables in M33. I. Evidence For a Field Halo Population
• A Catalog of Star Cluster Candidates in M33
• On The Origin of the Blue Tilt in Extragalactic Globular Cluster Systems
• Spectral Energy Distributions and Age Estimates of 39 Globular Clusters in M31
• New age estimates of M31 globular clusters from multi-colour photometry
• A Catalog of New M33 Star Clusters Based on the HST/WFPC2 Images
• Ages of M33 Star Clusters Based on the HST/WFPC2 Photometry
• Spectral Energy and Age Distributions for 51 Globular Cluster Candidates

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