Interstellar Medium Disruption in the Centaurus A Group

Abstract

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 MH I = 4 × 105 and 2.1 × 107 M⊙ and 0.04M⊙ L⊙,B-1 < MHI/LB < 1.81 M⊙ L-1⊙,B The other 13 have upper limits between MHI = 5 × 105 and 4 × 106 M⊙ (MH I /LB < 0.24 M⊙ L⊙,B-1). 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 MB = -13 have either MH I > 107 or MH I < 106 M⊙. This gap may be explained by the ram pressure stripping mechanism at work in this dense environment in which all galaxies with MH I < 107 M⊙ have been stripped of their gas. The required intergalactic medium density to achieve this is ̃10-3 cm-3. Show more