Program: GS-2007B-Q-227

Dwarf galaxies are the most numerous by galaxy number in the universe, and their evolution is a vital ingredient within models of galaxy formation and evolution. Environment may play a role in the "intrinsic" evolution of dwarf galaxies, as gas-rich dwarfs can be converted to gas-poor dwarfs. The study of "transition-type" dwarfs with properties common to both gas-rich and gas-poor dwarfs will provide important clues about processes which transform one dwarf galaxy type to another. Transition-type dwarfs may be more numerous in higher-density environments. The Centaurus A and the Sculptor groups are nearby groups of galaxies, exhibiting different global properties. From both groups, we have selected 11 dwarf galaxies previously identified as gas-poor dwarfs. However, these galaxies have significant HI gas masses in the range between few 1e5 and few 1e7 solar masses. With gas-to-light ratios approaching those of gas-rich dwarfs, there may be present-day star formation within transition-type dwarfs. We request 9.8 hr with GMOS to image 11 transition-type dwarf galaxies with the Ha line- and continuum-filters in order to detect and measure the presence of H II regions, and to derive their rates of current star formation and gas-consumption timescales.