AAS 205th Meeting, 9-13 January 2005
Session 23 Globular Clusters in and around the Milky Way
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

## [23.10] Spitzer Space Telescope IRAC Imagery of Omega Centauri

M.L. Boyer, C.E. Woodward, R.D. Gehrz, E. Polomski (University of Minnesota), J.Th. van Loon, A. Evans (Keele University)

Because of their high stellar density and well determined distances, globular clusters (GCs) offer the perfect laboratory for studies of stellar evolution. As a star loses mass through winds, it enriches the intra-cluster medium (ICM), which is stripped away when the GC passes through the galactic plane. This in turn enriches the ISM in the galactic plane, which may induce stellar formation. We have obtained Spitzer Space Telescope IRAC images of one quadrant (~ 10 arcmin \times 5 arcmin area) of the globular cluster Omega Cen at 3.6, 4.5, 5.8, and 8.0 microns. We present a preliminary analysis of color-magnitude diagrams of the Spitzer data and discuss the detectability of the ICM in this cluster. At least five red giant stars with circumstellar emission near the tip-AGB luminosity have been detected, along with the tip of the RGB. If the circumstellar emission of the red stars includes dust, this indicates mass loss, which may be correlated to metallicity. Studying the mass loss characteristics of these stars and the ICM of Omega Cen may improve our understanding of the impact of solar mass stars and of GCs on the chemical evolution of the Milky Way galaxy.

This work is supported in part by NASA (JPL/SSC - 1256406 and 1215746).

Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.