Stellar populations in the ELT perspective

We discuss the impact that the next generation of Extremely Large Telescopes will have on the open astrophysical problems of resolved stellar populations. In particular, we address the interplay between multiband photometry and spectroscopy.Comment: 6 pages, 3 figures. To appear in the proceedings of "EWASS 2013 Symposium 5: Local Group, Local Cosmology," (8-9 July 2013, Turku, Finland), Mem. S.A.It, M. Monelli and S. Salvadori Ed

Boo-1137 - An Extremely Metal-Poor Star in the Ultra-Faint Dwarf Spheroidal Galaxy Bo\"{o}tes I

We present high-resolution, high-S/N spectra of an extremely metal- poor giant star Boo-1137 in the "ultra-faint" dwarf spheroidal galaxy (dSph) Bootes I (absolute magnitude Mv ~ -6.3). With [Fe/H] = -3.7, this the most metal-poor star yet identified in an ultra-faint dSph. Comparison of relative abundances, [X/Fe], for some 15 elements with those of the extremely metal-poor giants of the Galactic halo shows Boo-1137 is "normal" with respect to C and N, the odd-Z elements Na and Al, the Fe-peak elements, and the n-capture elements Sr and Ba, in comparison with the bulk of the halo with [Fe/H] < -3.0. The alpha- elements Mg, Si, Ca, and Ti are all higher by Delta[X/Fe] ~ 0.2 than average halo values. Monte-Carlo analysis indicates Delta[alpha/Fe] values this large are expected with probability ~ 0.02. The abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in Fe abundances we reported earlier. The similarity of most of the Boo-1137 relative abundances with respect to halo values, and the fact that the alpha-elements are all offset by a similar small amount from the halo averages, points to the same underlying galaxy-scale stellar initial mass function, but that Boo-1137 likely originated in a star-forming region where the abundances reflect either poor mixing of supernova (SN) ejecta, or poor sampling of the SN progenitor mass range, or both.Comment: 33 pages, 6 figures, submitted to Astrophysical Journa

On the He burning phases of the Carina dSph

We performed a detailed comparison between predicted He burning phases and multiband photometry of the Carina dwarf spheroidal galaxy. We found a good agreement with the predictions computed assuming an alpha -enhanced chemical mixture, indicating a mean metallicity {[Fe/H]}̃-1.8 with a raw observed peak-to-peak spread in iron abundance of 0.4±0.2 dex