AAS 201st Meeting, January, 2003
Session 13. Galaxy - Structure
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[13.06U] A Warp in the Large Magellanic Cloud Disk?

C. Salyk (MIT), K.A.G. Olsen (CTIO, NOAO)

We present a study of the shape of the Large Magellanic Cloud (LMC) disk. We observed 50 LMC fields in V and I with the Cerro Tololo Inter-American Observatoryís 0.9-meter telescope. After performing psf photometry and plotting the stars on V-I vs. I color-magnitude diagrams, we isolated the red clump stars on each frame and determined the brightness of the clump in each field. We used the color of the clump to correct for extinction. To determine the inclination of the LMC, we attempted to fit a plane to a plot of brightness of the red clump versus position in the sky. However, we first found it necessary to exclude 15 fields in the southwest of the LMC, which have red clump magnitudes ~0.1 mag brighter than the fitted plane. We find inclination and position angle, respectively, to be, i = 35\arcdeg.8 ± 2\arcdeg.4 and \theta = 145\arcdeg ± 4\arcdeg. We attribute the southwestern deviation to this fitted plane to be evidence that the LMC disk is warped and twisted, containing features that extend up to 2.5 kpc out of the plane. We argue that alternative ways of producing red clump stars brighter than expected, such as variations in age and metallicity of the stars, are unlikely to explain our observations. This work was supported by the National Science Foundationís Research Experiences for Undergraduates site grant to Cerro Tololo Interamerican Observatory.

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