1999/09/13 by A. M. Piersimoni, Piersimoni, A. M., G. Bono +11
Physics and Astronomy · #Adaptive optics and wavefront sensing #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9909198
7 pages, 2 postscript figures, accepted for publication on A&A Letters
arxiv created 1999/09/13 · openalex publication_date 1999/09/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 RGB, and a sample of bright blue stars, belonging to a young stellar component. The comparison between theory and observations confirms that this sample of bright stars is consistent with the occurrence of a star formation episode ≈0.1 Gyr ago. In agreement with previous investigations (Sarajedini et al. 1997; Aparicio et al. 1997), we also find that this young stellar population is more centrally concentrated than the old one. By adopting the new calibration of the Tip of the RGB (TRGB) provided by Salaris & Cassisi (1998) we estimated that the Antlia distance modulus is (m-M)0=25.89±0.10 mag, and therefore a distance D=1.51± 0.07 Mpc. This distance determination is ≈13% larger than the values suggested in previous investigations. By adopting the calibration of the RGB (V-I) color index as a function of the metallicity, we estimated that the mean metallicity of Antlia stellar population is of the order of [Fe/H]≈-1.3. The differential RGB luminosity function shows an excess in the observed counts -at the 2σ level- when compared with theoretical predictions. Plain arguments on the dependence of the TRGB luminosity on stellar age suggest that this discrepancy might be due to a stellar component with an age approximately equal to 0.7 Gyr.