GAS-BEARING EARLY-TYPE DWARF GALAXIES IN VIRGO: EVIDENCE FOR RECENT ACCRETION

Abstract

We investigate the dwarf (M_B> -16) galaxies in the Virgo cluster in the\nradio, optical, and ultraviolet regimes. Of the 365 galaxies in this sample, 80\nhave been detected in HI by the Arecibo Legacy Fast ALFA survey. These\ndetections include 12 early-type dwarfs which have HI and stellar masses\nsimilar to the cluster dwarf irregulars and BCDs. In this sample of 12, half\nhave star-formation properties similar to late type dwarfs, while the other\nhalf are quiescent like typical early-type dwarfs. We also discuss three\npossible mechanisms for their evolution: that they are infalling field galaxies\nthat have been or are currently being evolved by the cluster, that they are\nstripped objects whose gas is recycled, and that the observed HI has been\nrecently reaccreted. Evolution by the cluster adequately explains the\nstar-forming half of the sample, but the quiescent class of early-type dwarfs\nis most consistent with having recently reaccreted their gas.\n