The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205

Broadband near-infrared images are used to probe the photometric properties of the brightest asymptotic giant branch (AGB) stars within 2' of the centers of the dwarf elliptical galaxies NGC 147, NGC 185, and NGC 205. Sequences originating from oxygen-rich M giants and C stars are clearly distinguished on the (K, H - K) and (K, J - K) color-magnitude diagrams. Based on the peak brightness and color of the M giant sequences, ages of 1 and 0.1 Gyr are predicted for the most recent significant star-forming events in NGC 185 and NGC 205, respectively. The bolometric luminosity function of M giants in NGC 205 is flatter than in NGC 185, in agreement with studies at wavelengths shortward of 1 mm. The most luminous AGB stars in NGC 147 are well mixed with fainter stars throughout the area surveyed in this galaxy, and the peak brightness of the M giant sequence indicates that the most recent significant star-forming activity occurred ~3 Gyr in the past.