V and I Photometry of Bright Giants in the Central Regions of NGC 147

Abstract

Deep V and I CCD images with sub-arcsec spatial resolution are used to investigate the stellar content of the central regions of the Local Group dwarf elliptical galaxy NGC147. Red giant branch (RGB) stars are resolved over the entire field, and the RGB-tip occurs at I ~ 20.5, suggesting that the distance modulus is 24.3. A comparison with globular cluster sequences indicates that the center of NGC147 is moderately metal-poor, with [Fe/H] ~ -1. This is not significantly different from what was found in the outer regions of the galaxy by Mould, Kristian & Da Costa (1983, ApJ, 270, 471). Moreover, the width of the V-I color distribution at I = 21.0 indicates that a spread in metallicity is present, with sigma[Fe/H] ~ +/- 0.3. There is no evidence of a component more metal-poor than [Fe/H] ~ -1.3. A small population of moderately bright asymptotic giant branch (AGB) stars has also been detected, and the AGB-tip occurs near M{bol} ~ -5.0, indicating that an intermediate-age population is present. It is estimated that the intermediate-age population contributes ~ 2-3% of the V light from NGC147.