Deep griz GMOS Imaging of the Dwarf Irregular Galaxy Kar 50

Abstract

Images obtained with the Gemini Multi-Object Spectrograph (GMOS) are used to investigate the stellar content and distance of the dwarf irregular galaxy Kar 50. The brightest object is an HII region, and the bright stellar content is dominated by stars with g'-r' < 0. The tips of the main sequence and the red giant branch are tentatively identified near r' = 24.9 and i' = 25.5, respectively. The galaxy has a blue integrated color with no significant color gradient, and we conclude that Kar 50 has experienced a recent galaxy-wide episode of star formation. The distance estimated from the brightest blue stars indicates that Kar 50 is behind the M81 group, and this is consistent with the tentative RGB-tip brightness. Kar 50 has a remarkably flat central surface brightness profile, even at wavelengths approaching 1um, although there is no evidence of a bar. In the absence of another large star-forming episode, Kar 50 will evolve into a very low surface brightness galaxy.Comment: 17 pages of text and 8 postscript figures. Accepted for publication in the PAS