Abstract: Dwarf galaxies constitute the most numerous extragalactic population in the local universe and can thus place constraints galaxy formation. Gas-deficient dwarfs with little to no recent star formation dominate the Local Group but a few faint, HI-bearing dwarfs like Leo T have been discovered in the outskirts of the Milky Way's influence. ALFALFA, an ongoing blind HI survey, has found a significant population of low surface brightness dwarfs missed by previous optical surveys suggesting that these systems may represent a so far poorly studied population of widely distributed, optically faint yet gas-bearing dwarf. In this talk I will present our current understanding of the contribution of gas-bearin dwarfs to cosmology at z=0. Can they solve the substructure problem? How significant is the role of environment in their formation? What fraction of dwarfs have been formed from tidal debris?<br>
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