Surveying the agents of galaxy evolution in the tidally stripped, low metallicity Small Magellanic Cloud (SAGE-SMC). II. Cool evolved stars

Martha L. Boyer, Sundar Srinivasan, Jacco Th Van Loon, Iain McDonald, Margaret Meixner, Dennis Zaritsky, Karl D. Gordon, F. Kemper, Brian Babler, Miwa Block, Steve Bracker, Charles W. Engelbracht, Joe Hora, Remy Indebetouw, Marilyn Meade, Karl Misselt, Thomas Robitaille, Marta Sewiło, Bernie Shiao, Barbara Whitney

Research output: Contribution to journalArticle

102 Scopus citations

Abstract

We investigate the infrared (IR) properties of cool, evolved stars in the Small Magellanic Cloud (SMC), including the red giant branch (RGB) stars and the dust-producing red supergiant (RSG) and asymptotic giant branch (AGB) stars using observations from the Spitzer Space Telescope Legacy program entitled "Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity SMC," or SAGE-SMC. The survey includes, for the first time, full spatial coverage of the SMC bar, wing, and tail regions at IR wavelengths (3.6-160 μm). We identify evolved stars using a combination of near-IR and mid-IR photometry and point out a new feature in the mid-IR color-magnitude diagram that may be due to particularly dusty O-rich AGB stars. We find that the RSG and AGB stars each contribute ≈ 20% of the global SMC flux (extended + point-source) at 3.6 μm, which emphasizes the importance of both stellar types to the integrated flux of distant metal-poor galaxies. The equivalent SAGE survey of the higher-metallicity Large Magellanic Cloud (SAGE-LMC) allows us to explore the influence of metallicity on dust production. We find that the SMC RSG stars are less likely to produce a large amount of dust (as indicated by the [3.6] - [8] color). There is a higher fraction of carbon-rich stars in the SMC, and these stars appear to reach colors as red as their LMC counterparts, indicating that C-rich dust forms efficiently in both galaxies. A preliminary estimate of the dust production in AGB and RSG stars reveals that the extreme C-rich AGB stars dominate the dust input in both galaxies, and that the O-rich stars may play a larger role in the LMC than in the SMC.

Original languageEnglish (US)
Article number103
JournalAstronomical Journal
Volume142
Issue number4
DOIs
StatePublished - Oct 1 2011

Keywords

  • Magellanic Clouds
  • circumstellar matter
  • stars: AGB and post-AGB
  • stars: carbon
  • stars: mass-loss
  • supergiants

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Boyer, M. L., Srinivasan, S., Van Loon, J. T., McDonald, I., Meixner, M., Zaritsky, D., Gordon, K. D., Kemper, F., Babler, B., Block, M., Bracker, S., Engelbracht, C. W., Hora, J., Indebetouw, R., Meade, M., Misselt, K., Robitaille, T., Sewiło, M., Shiao, B., & Whitney, B. (2011). Surveying the agents of galaxy evolution in the tidally stripped, low metallicity Small Magellanic Cloud (SAGE-SMC). II. Cool evolved stars. Astronomical Journal, 142(4), [103]. https://doi.org/10.1088/0004-6256/142/4/103