1999A&A...352L..63P

We present deep (I,V-I) and (I,B-I) color-magnitude diagrams (CMDs) of the Antlia dwarf galaxy, based on Science Verification (SV) data collected with the FORS I camera on the ESO Very Large Telescope (VLT). The CMDs present two key features: a well-defined Red Giant Branch (RGB), and a sample of bright blue stars, belonging to a young stellar component. The comparison between theory and observations confirms that the bright stars are consistent with the occurrence of a star formation episode ≃0.1Gyr ago. In agreement with Sarajedini et al. (1997AJ....114.2505S) and Aparicio et al. (1997AJ....114.1447A), we find that the young stars are more centrally concentrated than the old ones. By adopting the new calibration of the Tip of the RGB (TRGB) provided by Salaris & Cassisi (1998MNRAS.298..166S) we estimated that the Antlia distance modulus is (m-M)₀=25.89±0.10mag, and therefore a distance D=1.51±0.07Mpc. This distance determination is ≃13% larger than the values suggested in previous investigations. We estimated that the mean metallicity of Antlia is of the order of [Fe/H]≃-1.3. This estimate is at least 0.3dex more metal-rich than similar evaluations available in the literature. The disagreement both in the distance and in the metallicity determinations are mainly due to difference in the calibration of the TRGB method and in the (V-I) color index vs. metallicity relation. The differential RGB luminosity function shows an excess in the observed counts -at the 2σ level- when compared with theoretical predictions. This discrepancy might be due to a stellar component with an age approximately equal to 0.7Gyr.