The Star Clusters of the Small Magellanic Cloud: Age Distribution

We present age measurements for 195 star clusters in the Small Magellanic Cloud based on comparison of integrated colors measured from the Magellanic Clouds Photometric Survey with models of simple stellar populations. We find that the modeled nonuniform changes of cluster colors with age can lead to spurious age peaks in the cluster age distribution; that the observed numbers of clusters with age t declines smoothly as t-2.1; that for an assumed initial cluster mass function scaling as M-2, the dependence of the cluster disruption time on mass is proportional to M0.48; that despite the apparent abundance of young clusters, the dominant epoch of cluster formation was the initial one; and that there are significant differences in the spatial distribution of clusters of different ages. Because of limited precision in our age measurements, we cannot address the question of detailed correspondence between the cluster age function and the field star formation history. However, this sample provides an initial guide as to which clusters to target in more detailed studies of specific age intervals.

[1]  D. Zaritsky,et al.  Quantifying the Drivers of Star Formation on Galactic Scales. I. The Small Magellanic Cloud , 2003, astro-ph/0312127.

[2]  D. Zaritsky,et al.  The Star Formation History of the Small Magellanic Cloud , 2003, astro-ph/0312100.

[3]  T. J. Dupuy,et al.  Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading and Size-of-Sample Effects , 2003, astro-ph/0306528.

[4]  Cambridge,et al.  Star cluster formation and evolution in nearby starburst galaxies — I. Systematic uncertainties , 2003, astro-ph/0302286.

[5]  Peter Anders,et al.  Spectral and photometric evolution of young stellar populations: The impact of gaseous emission at various metallicities , 2003, astro-ph/0302146.

[6]  N. Bastian,et al.  Clusters in the inner spiral arms of M 51: The cluster IMF and the formation history , 2002, astro-ph/0210594.

[7]  S. Boutloukos,et al.  Star cluster formation and disruption time-scales — I. An empirical determination of the disruption time of star clusters in four galaxies , 2002, astro-ph/0210595.

[8]  E. Grebel,et al.  The Magellanic Clouds Photomtric Survey: The Small Magellanic Cloud Stellar Catalog and Extinction Map , 2001, astro-ph/0110665.

[9]  R. Rich,et al.  New Photometry for the Intermediate-Age Large Magellanic Cloud Globular Cluster NGC 2121 and the Nature of the LMC Age Gap , 2001, astro-ph/0105546.

[10]  D. Geisler,et al.  Ages and Metallicities of Five Intermediate-Age Star Clusters Projected Towards the Small Magellanic Cloud , 2001, astro-ph/0103490.

[11]  E. Bica,et al.  Morphologies and ages of star cluster pairs and multiplets in the Small Magellanic Cloud , 2000, astro-ph/0006369.

[12]  E. Grebel,et al.  The Morphologies of the Small Magellanic Cloud , 2000, The Astrophysical journal.

[13]  E. Bica,et al.  Updating the Census of Star Clusters in the Small Magellanic Cloud , 1999, astro-ph/9912386.

[14]  S. M. Fall,et al.  The Mass Function of Young Star Clusters in the “Antennae” Galaxies , 1999, The Astrophysical journal.

[15]  D. Zaritsky Dust and Stellar Populations in the Large Magellanic Cloud , 1999, astro-ph/9908363.

[16]  S. M. Fall,et al.  The Luminosity Function of Young Star Clusters in “the Antennae” Galaxies (NGC 4038/4039) , 1999, astro-ph/9907430.

[17]  S. M. Fall,et al.  Two Groups of Nearly Coeval Star Clusters in the Small Magellanic Cloud , 1999, astro-ph/9907398.

[18]  Denis Foo Kune,et al.  Starburst99: Synthesis Models for Galaxies with Active Star Formation , 1999, astro-ph/9902334.

[19]  R. S. French,et al.  WFPC2 Observations of Star Clusters in the Magellanic Clouds. II. The Oldest Star Clusters in the Small Magellanic Cloud , 1998, astro-ph/9808091.

[20]  P. Wozniak,et al.  The Optical Gravitational Lensing Experiment. The Catalog of Clusters in the Small Magellanic Cloud , 1998, astro-ph/9806321.

[21]  D. Hatzidimitriou,et al.  Ca II Triplet Spectroscopy of Giants in Small Magellanic Cloud Star Clusters: Abundances, Velocities, and the Age-Metallicity Relation , 1998, astro-ph/9802008.

[22]  B. Pagel,et al.  Chemical evolution of the Magellanic Clouds: analytical models , 1998, astro-ph/9801221.

[23]  B. Westerlund The Magellanic Clouds , 1997 .

[24]  H. Schmitt,et al.  A Revised and Extended Catalog of Magellanic System Clusters, Associations, and Emission Nebulae. I. Small Magellanic Cloud and Bridge , 1995 .

[25]  Stephen A. Shectman,et al.  THE GREAT-CIRCLE CAMERA: A NEW DRIFT-SCANNING INSTRUMENT , 1995, astro-ph/9509017.

[26]  C. Leitherer,et al.  Hubble Space Telescope discovery of candidate young globular clusters in the merger remnant NGC 7252 , 1993 .

[27]  Edward J. Shaya,et al.  Planetary Camera observations of NGC 1275 - Discovery of a central population of compact massive blue star clusters , 1992 .

[28]  S. Bergh Star clusters in the clouds of Magellan , 1991 .

[29]  J. Mould,et al.  The continuity of cluster formation in the Large Magellanic Cloud , 1988 .

[30]  P. Hodge CLUSTERS OF THE SMALL MAGELLANIC CLOUD. II. AGE DISTRIBUTIONS. , 1987 .

[31]  P. Hodge CLUSTERS OF THE SMALL MAGELLANIC CLOUD. I. A CATALOG OF 213 NEW CLUSTERS. , 1986 .

[32]  H. Ford,et al.  Kinematics and internal dynamics of planetary nebulae in the small Magellanic Cloud , 1985 .

[33]  P. Hodge THE STELLAR ASSOCIATIONS OF THE SMALL MAGELLANIC CLOUD. , 1985 .

[34]  R. Schild Interstellar reddening law. , 1977 .

[35]  P. Szkody,et al.  Ages of star clusters in a section of the Large Magellanic Cloud , 1974 .

[36]  P. Hodge,et al.  Catalog of 86 new star clusters in the Small Magellanic Cloud. , 1974 .

[37]  P. Hodge Studies of the Large Magellanic Cloud. V. The Young Populous Clusters. , 1961 .

[38]  E. M. Lindsay The Cluster System of the Small Magellanic Cloud , 1958 .

[39]  G. Kron STAR CLUSTERS IN THE SMALL MAGELLANIC CLOUD: I. IDENTIFICATION OF 69 CLUSTERS , 1956 .

[40]  D. Costa The age-abundance relations and age distributions for the star clusters of the Magellanic Clouds , 1991 .