大双筒望远镜观测到的犬座Venaeu I矮星系
A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy
摘要：
我们提出了第一个深色星等图的犬Venaushi（CVnI）矮星系的观测与宽视场大双筒望远镜的大双筒相机。深入到最老恒星的主序转折点，它揭示了CVnI的恒星星族的二分法：它拥有一个古老的（> 10 Gyr），金属贫乏（[Fe/H]~-2.0）和空间扩展的人口以及一个更年轻的（~1.4 - 2.0 Gyr），0.5 dex更多的金属，空间更集中的人口。这些年轻的恒星也在星系中心以东偏移64_{-20}^{+40} pc。这些数据表明，这个年轻的群体，代表了银河系半光半径内恒星质量的约3 - 5%，应该与Ibata等人（2006）发现的运动学冷恒星成分相一致。因此，CVnI遵循的行为，其他远程MW矮椭球体都包含中间年龄和/或年轻的人口：一个复杂的恒星形成历史是可能的，在极低质量的星系。
英文摘要：
We present the first deep color-magnitude diagram of the Canes Venatici I (CVnI) 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 CVnI: 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 64_{-20}^{+40} pc to the East of the galaxy center. The data suggest that this young population, which represent ~ 3-5 % of the stellar mass of the galaxy within its half-light radius, should be identified with the kinematically cold stellar component found by Ibata et al. (2006). CVnI 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.
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