The Spitzer Survey of the Small Magellanic Cloud:: S3MC imaging and photometry in the mid- and far-infrared wave bands

We present the initial results from the Spitzer Survey of the Small Magellanic Cloud ( (SMC)-M-3), which imaged the star- forming body of the SMC in all seven MIPS and IRAC wave bands. 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 mu m 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 similar to 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 mu m 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 less than or similar to [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-O9) with a large 24 mu m excess. This excess is reminiscent of debris disks and is detected in only a small fraction of these stars ( less than or similar to 5%). The majority of the brightest infrared point sources in the SMC fall into groups 1-3. We use this photometric information to produce a catalog of 282 bright YSOs in the SMC with a very low level of contamination ( similar to 7%).