AN INFRARED CENSUS OF DUST IN NEARBY GALAXIES WITH SPITZER (DUSTiNGS). II. DISCOVERY OF METAL-POOR DUSTY AGB STARS
- Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street SE, University of Minnesota, Minneapolis, MN 55455 (United States)
- Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada)
- IAASARS, National Observatory of Athens, GR-15236 Penteli (Greece)
- STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels (Belgium)
- Laboratoire Lagrange, UMR7293, Univ. Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d'Azur, F-06300 Nice (France)
- ESA-European Space Astronomy Centre, Apdo. de Correo 78, E-28691 Villanueva de la Cañada, Madrid (Spain)
- Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
- Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom)
- Astronomy Department, Cornell University, Ithaca, NY 14853-6801 (United States)
The DUSTiNGS survey (DUST in Nearby Galaxies with Spitzer) is a 3.6 and 4.5 μm imaging survey of 50 nearby dwarf galaxies designed to identify dust-producing asymptotic giant branch (AGB) stars and massive stars. Using two epochs, spaced approximately six months apart, we identify a total of 526 dusty variable AGB stars (sometimes called ''extreme'' or x-AGB stars; [3.6]-[4.5] > 0.1 mag). Of these, 111 are in galaxies with [Fe/H] < –1.5 and 12 are in galaxies with [Fe/H] < –2.0, making them the most metal-poor dust-producing AGB stars known. We compare these identifications to those in the literature and find that most are newly discovered large-amplitude variables, with the exception of ≈30 stars in NGC 185 and NGC 147, 1 star in IC 1613, and 1 star in Phoenix. The chemical abundances of the x-AGB variables are unknown, but the low metallicities suggest that they are more likely to be carbon-rich than oxygen-rich and comparisons with existing optical and near-IR photometry confirm that 70 of the x-AGB variables are confirmed or likely carbon stars. We see an increase in the pulsation amplitude with increased dust production, supporting previous studies suggesting that dust production and pulsation are linked. We find no strong evidence linking dust production with metallicity, indicating that dust can form in very metal-poor environments.
- OSTI ID:
- 22364206
- Journal Information:
- Astrophysical Journal, Vol. 800, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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