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  • Bolatto, Alberto D; Simon, Joshua D; Stanimirovic, Snezana; van Loon, Jacco Th; Shah, Ronak Y; Venn, Kim; Leroy, Adam K; Sandstrom, Karin; Jackson, James M; Israel, Frank P; Li, Aigen; Staveley-Smith, Lister; Bot, Caroline; Boulanger, Francois; Rubio, Monica

    arXiv.org, 08/2006
    Paper

    We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S3MC), which imaged the star-forming body of the Small Magellanic Cloud (SMC) in all seven MIPS and IRAC wavebands. We find that the F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and takes a wide range of values that are unrelated to metallicity but anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that photodestruction is primarily responsible for the low abundance of PAHs observed in star-forming low-metallicity galaxies. We use the S3MC images to compile a photometric catalog of ~400,000 mid- and far-infrared point sources in the SMC. The sources detected at the longest wavelengths fall into four main categories: 1) bright 5.8 um sources with very faint optical counterparts and very red mid-infrared colors (5.8-8.0>1.2), which we identify as YSOs. 2) Bright mid-infrared sources with mildly red colors (0.16<5.8-8.0<0.6), identified as carbon stars. 3) Bright mid-infrared sources with neutral colors and bright optical counterparts, corresponding to oxygen-rich evolved stars. And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This excess is reminiscent of debris disks, and is detected in only a small fraction of these stars (<5%). The majority of the brightest infrared point sources in the SMC fall into groups one to three. We use this photometric information to produce a catalog of 282 bright YSOs in the SMC with a very low level of contamination (~7%).