A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy

TL;DR

This study provides the first deep color-magnitude diagram of the Canes Venatici I dwarf galaxy, revealing a complex stellar population with both old and young stars, indicating a varied star formation history.

Contribution

It presents the first detailed analysis of CVnI's stellar populations using deep imaging, uncovering a spatial and age-based dichotomy in its stars.

Findings

Discovery of an old, metal-poor, extended population.

Identification of a younger, more metal-rich, concentrated population.

Young stars are offset by approximately 64 pc east of the galaxy center.

Abstract

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.