ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. II. OPTICAL IMAGING OBSERVATIONS

We present results from ground-based optical imaging of a low-mass dwarf galaxy discovered by the ALFALFA 21 cm Hi survey. Broadband (BVR) data obtained with theWIYN 3.5mtelescope at Kitt Peak National Observatory (KPNO) are used to construct color-magnitude diagrams of the galaxy's stellar population down to V sub(o) ~ 25. We also use narrowband H alpha imaging from the KPNO 2.1 m telescope to identify a HII region in the galaxy. We use these data to constrain the distance to the galaxy to be between 1.5 and 2.0 Mpc. This places Leo P within the Local Volume but beyond the Local Group. Its properties are extreme: it is the lowest-mass system known that contains significant amounts of gas and is currently forming stars.