THE UNIVERSAL INITIAL MASS FUNCTION IN THE EXTENDED ULTRAVIOLET DISK OF M83

• Published in: The Astrophysical journal Vol. 749; no. 1; pp. 1 - 10
• Main Authors: KODA, Jin, YAGI, Masafumi, BOISSIER, Samuel, DE PAZ, Armando Gil, IMANISHI, Masatoshi, DONOVAN MEYER, Jennifer, MADORE, Barry F, THILKER, David A
• Format: Journal Article
• Language: English
• Published: Bristol IOP 10.04.2012; American Astronomical Society
• Subjects: Astronomy; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Clusters; Disks; Dust; Earth, ocean, space; ENERGY SPECTRA; Exact sciences and technology; Extinction; EXTREME ULTRAVIOLET RADIATION; Formations; GALACTIC EVOLUTION; Initial mass function; LUMINOSITY; MAGELLANIC CLOUDS; MASS; Sciences of the Universe; STAR CLUSTERS; STARS; STOCHASTIC PROCESSES; Ultraviolet; B stars; O stars; Young cluster; Galaxies; H-alpha lines; Spectral energy distribution; galaxies: individual (M83); stars: luminosity function, mass function; Star clusters; Star models; Formation rate; Massive stars; Galaxy clusters; Mass function; Stellar mass; Metallicity; Small Magellanic Cloud; Stellar population; Initial mass function; Extinction curve; galaxies: star clusters: general; GALEX satellite; Luminosity function
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637x/749/1/20

We report deep Subaru H alpha observations of the extended ultraviolet (XUV) disk of M83. These new observations enable the first complete census of very young stellar clusters over the entire XUV disk. Combining Subaru and Galaxy Evolution Explorer data with a stellar population synthesis model, we find that (1) the standard, but stochastically sampled, initial mass function (IMF) is preferred over the truncated IMF because there are low-mass stellar clusters (10 super(2-3) M sub([middot in circle])) that host massive O-type stars; (2) the standard Salpeter IMF and a simple aging effect explain the counts of far-UV (FUV)-bright and H alpha -bright clusters with masses >10 super(3) M sub([middot in circle]); and (3) the H alpha -to-FUV flux ratio over the XUV disk supports the standard IMF. To reach conclusion (2), we assumed instantaneous cluster formation and a constant cluster formation rate over the XUV disk. The Subaru Prime Focus Camera covers a large area even outside the XUV disk-far beyond the detection limit of the H I gas. This enables us to statistically separate the stellar clusters in the disk from background contamination. The new data, model, and previous spectroscopic studies provide overall consistent results with respect to the internal dust extinction (A sub(V) ~ 0.1 mag) and low metallicity (~0.2 Z sub([middot in circle])) using the dust extinction curve of the Small Magellanic Cloud. The minimum cluster mass for avoiding the upper IMF incompleteness due to stochastic sampling and the spectral energy distributions of O, B, and A stars are discussed in the Appendices.