2007AJ....133..261B

We present the results of a 21 cm neutral hydrogen (H I) line detection experiment in the direction of 18 low-luminosity dwarf galaxies of the Centaurus A group, using the Australia Telescope National Facility 64 m Parkes Radio Telescope and the Australia Telescope Compact Array. Five dwarfs have H I masses between M_HI_=4x10⁵ and 2.1x10⁷ M_☉and 0.04 M_☉L^–1_☉,B<M_HI_/LB_<1.81 M_☉L^–1_☉,B. The other 13 have upper limits between M_HI_=5x10⁵ and 4x10⁶ M_☉ (M_HI_/LB_<0.24 M_☉L^–1_☉,B). Two of the mixed-morphology dwarfs remain undetected in H I, a situation that is in contrast to that of similar Local Group and Sculptor group objects, which all contain significant amounts of neutral gas. There is a discontinuity in the H I properties of Centaurus A group low-luminosity dwarfs that is unobserved among Sculptor group dwarfs. All objects fainter than M_B=-13 have either M_HI_>10⁷ or M_HI_<10⁶ M_☉. This gap may be explained by the ram pressure stripping mechanism at work in this dense environment in which all galaxies with M_HI_<10⁷ M_☉have been stripped of their gas. The required intergalactic medium density to achieve this is ∼10^–3/cm3.