Program: GS-2006A-Q-45

Disk galaxies tend to be immersed in a richly-populated envelope that has been associated with merging activity during intermediate epochs. However, the majority of the galaxies that have been studied to date are undisturbed and `normal??, and so are not well suited for determining if envelope formation continues to the present day. I propose to use GMOS on Gemini South to obtain moderately deep r?? and i' images that sample the outer regions of the Centaurus Group galaxies NGC 4945, NGC 5102, and NGC 5253. These are relatively bright, disk-dominated galaxies that span a range of morphologies, and show signs of nuclear star formation. The systems are viewed at oblique angles, which is important for suppressing contamination from the thin disk. The r?? and i?? images will be used (1) to measure the mean metallicity and metallicity dispersion in the outer regions of these galaxies, and (2) to search for luminous AGB stars.