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A Deep Large Binocular Telescope View of the Canes Venatici I Dwarf Galaxy

2007; IOP Publishing; Volume: 672; Issue: 1 Linguagem: Inglês

10.1086/525559

1538-4357

Nicolas F. Martin, Matthew G. Coleman, J. T. A. de Jong, Hans-Walter Rix, Eric F. Bell, David J. Sand, John M. Hill, D. J. Thompson, V. Burwitz, E. Giallongo, Roberto Ragazzoni, Emiliano Diolaiti, F. Gasparo, A. Grazian, Fernando Pedichini, Jill Bechtold,

Gamma-ray bursts and supernovae

We present the first deep color-magnitude diagram of the Canes Venatici I (CVn I) dwarf galaxy from observations with the wide-field Large Binocular Camera on the Large Binocular Telescope. Reaching down to the main-sequence turnoff of the oldest stars, it reveals a dichotomy in the stellar populations of CVn I: it harbors an old (≳10 Gyr), metal-poor ([ Fe/H ] ∼ − 2.0), and spatially extended population along with a much younger (~1.4-2.0 Gyr), 0.5 dex more metal-rich, and spatially more concentrated population. These young stars are also offset by pc to the east of the galaxy center. The data suggest that this young population, which represents ~3%-5% of the stellar mass of the galaxy within its half-light radius, should be identified with the kinematically cold stellar component found in a recent spectroscopic survey. CVn I therefore follows the behavior of the other remote MW dwarf spheroidals, which all contain intermediate-age and/or young populations: a complex star formation history is possible in extremely low mass galaxies.