Oxygen-rich dust production in IC 10^⋆

¹ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot DAPNIA/Service d’Astrophysique, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: vianney.lebouteiller@cea.fr; vianney@isc.astro.cornell.edu
² Center for Radiophysics and Space Research, Cornell University, Space Sciences Building, Ithaca, NY 14853-6801, USA
³ Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussels, Belgium
⁴ Astrophysics Group, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁵ Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles St. Baltimore, MD 21218, USA
⁶ Department of Physics, United States Naval Academy, 572C Holloway Road, Annapolis, MD 21402, USA
⁷ Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville, VA 22904, USA
⁸ Institut d’Astrophysique Spatiale, CNRS/Université Paris-Sud 11, 91405 Orsay, France
⁹ Lowell Observatory, 1400 West Mars Hill Rd., Flagstaff, AZ 86001, USA
¹⁰ Sub-Department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK

Received: 24 July 2012
Accepted: 5 September 2012

Abstract

Context. We report the detection of oxygen-rich circumstellar envelopes in stars of the nearby (700 kpc) starburst galaxy IC 10. The star-formation history and the chemical environment of this galaxy make it an ideal target to observe dust production by massive stars in a metal-poor environment.

Aims. The goal of this study is to identify oxygen-rich stars in IC 10 and to constrain their nature between asymptotic giant branch stars (AGBs), red supergiants (RSGs), and other bright infrared sources. We examine the mass-loss rates of the stars and compare to results obtained for the Magellanic Clouds. Our objectives are to (1) assess whether RSGs can be significant dust producers in IC 10, and (2), solve the discrepancy between the star-formation history of IC 10 and the relatively low number of RSGs detected in the optical.

Methods. We search for silicate dust in emission by using the spectral map observed with the Infrared Spectrograph on board the Spitzer Space Telescope. The optical (UBVRI) and infrared (JHK, Spitzer/IRAC and Spitzer/MIPS) photometry are used to assert the membership of the stars to IC 10 and distinguish between AGBs and RSGs. Radiative models are used to infer mass-loss rates and stellar luminosities.

Results. The luminosity and colors of at least 9 silicate emission sources are consistent with stars within IC 10. Furthermore, the photometry of 2 of these sources is consistent with RSGs. We derive dust mass-loss rates similar to the values found in the Magellanic Clouds. Accounting for the sample completeness, RSGs are not important contributors to the dust mass budget in IC 10.