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The universal initial mass function in the extended ultraviolet disk of M83



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Koda, Jin and Yagi, Masafumi and Boissier, Samuel and Gil de Paz, Armando and Imanishi, Masatoshi and Meyer, Jennifer Donovan and Madore, Barry F. and Thilker, David A. (2012) The universal initial mass function in the extended ultraviolet disk of M83. Astrophysical journal, 749 (1). ISSN 0004-637X

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Official URL: http://dx.doi.org/10.1088/0004-637X/749/1/20


We report deep Subaru Hα 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 (10^2-3 M_☉) 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 Hα-bright clusters with masses >10^3 M_☉; and (3) the Hα-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 V ~ 0.1 mag) and low metallicity (~0.2 Z_☉) 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.

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© 2012. The American Astronomical Society. All rights reserved. We thank Sadanori Okamura and Tomoki Hayashino for providing the redshifted H-α filter for Suprime-Cam. J.K. thanks Peter Capak for his help with the IMCAT software and Deane Peterson and Fred Walter for discussion on stellar spectra. A.G.d.P is funded by the "Ramón y Cajal" program of the Spanish MICINN and partly supported by the AYA2009-10368 and Consolider-Ingenio 2010 CSD2006-70 projects. M.I. is supported by Grants-in-Aid for Scientific Research (No. 22012006, 23540273). Data analyses were in part carried out on the common use data analysis computer system at the Astronomical Data Center (ADC) of the National Astronomical Observatory of Japan. This work is based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts.

Uncontrolled Keywords:Star-formation; Hα; Standard stars; Local universe; Virgo cluster; Suprime-cam; Galaxies; Emission; Dust; Population
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35186
Deposited On:25 Jan 2016 14:04
Last Modified:10 Dec 2018 15:05

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