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K. B. W. McQuinn, C. E. Woodward, R. M. Humphreys, R. D. Gehrz, E. Polomski (University of Minnesota), Spitzer M33 Team
Our Local Group neighbor M33 provides an excellent laboratory for studying stellar populations and star formation across its well resolved and nearly face-on disk. Its southwest arm is a great example of a well-formed density wave and provides a unique opportunity to investigate dust lanes, HII regions, and stellar associations across and along the arm. We present a first look at the Spitzer Space Telescope infrared IRAC images (all bands) of M33's southwest spiral arm. The field was divided into 1.5' bins which is approximately 350 pc when projected at the distance of the galaxy. The 3.6 - 8.0 micron color-magnitude diagrams (CMDs) easily delineate the redder population while the 3.6 - 4.5 micron CMDs show normally behaved stars. The color-color plots assist in classifying the types of objects seen in the spiral arm. Preliminary results show that our multi-epoch data also identify stars with variability. We compare the M33 results with CMDs and color-color plots of IRAC field frames outside the Holmberg radius of the galaxy to identify field contamination in the images. This work is supported in part by NASA (JPL/SSC, contracts 1256406 and 1215746).
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.