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A.A. Cole (UMass)
The Large and Small Magellanic Clouds, as the nearest actively star-forming galaxies to the Milky Way, are vitally important objects to our understanding of stellar and galactic evolution in a complex environment. Their large angular extent has hampered global photometric studies until quite recently. The 2MASS survey, with its extraordinary photometric uniformity, provides a unique near-infrared window into the stellar demographics of the Magellanic Clouds and their habitat in the Milky Way halo.
We have used the (K, J-K) color-magnitude diagrams and the (J-H, H-K) color-color plots of the Clouds and the surrounding sky to deduce their geometry and internal structure. The spatial variation in color and magnitude of the tip of the red giant branch have been used to accurately determine the orientation of the stellar disk of the LMC, and to probe the extended structure of the SMC along the line of sight. Systematic variations of RGB color provide the first global view of the spatial variation in the shape of the Magellanic Cloud metallicity distribution functions.
The distinctive photometric signatures of late-type carbon stars also trace metallicity variations among the intermediate-age stellar populations, and provide luminous tracers of past dynamical interactions between the Clouds and the Milky Way.