Volume 385, Number 1, April I 2002
|Page(s)||21 - 31|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 April 2002|
Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 369167, Russia
2 Isaac Newton Institute, Chile, SAO Branch
3 Kitt Peak National Observatory, National Optical Astronomy Observatories, PO Box 26732, Tucson, AZ 85726, USA
4 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
5 Departamento de Física, Grupo de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
6 UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
7 Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA
8 Astronomical Observatory of Kiev University, 04053, Observatorna 3, Kiev, Ukraine
9 Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
10 Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109, USA
Corresponding author: I. D. Karachentsev, firstname.lastname@example.org
Accepted: 8 January 2002
We present Hubble Space Telescope/WFPC2 images of seventeen dwarf galaxies in the Centaurus A group. Their distances derived from the magnitudes of the tip of the red giant branch are 5.2 Mpc (KK112), 3.2 Mpc (ESO 321-014), 3.5 Mpc (KK179), 3.4 Mpc (NGC 5102), 4.6 Mpc (KK200), 3.7 Mpc (ESO 324-024), 4.7 Mpc (KK208), 4.6 Mpc (ESO 444-084), 4.4 Mpc (IC 4316), 4.5 Mpc (NGC 5264), 3.6 Mpc (KK211), 3.6 Mpc (KK213), 3.4 Mpc (ESO 325-011), 3.8 Mpc (KK217), 4.0 Mpc (KK221), 4.8 Mpc (NGC 5408), and 3.6 Mpc (PGC 51659). The galaxies are concentrated in two spatially separated groups around NGC 5128 = Cen A and NGC 5236 = M 83. The Cen A group itself has a mean distance of Mpc, a velocity dispersion of 89 km s-1, a mean projected radius of 263 kpc, an estimated orbital mass of , and an orbital mass-to-blue luminosity ratio of 64 . For the M 83 group we derived a mean distance of Mpc, a velocity dispersion of 62 km s-1, a mean projected radius of 142 kpc, an estimated orbital mass of , and . The M 83 group moves away from the Cen A group, which yields a radius of the zero-velocity surface of the Cen A group of Mpc. The total mass within , agrees with the orbital mass estimate. The centroids of both the groups have very small peculiar velocities, km s-1 (Cen A) and () km s-1 (M 83) with respect to the local Hubble flow with km s-1 Mpc-1.
Key words: galaxies: dwarf / galaxies: distances and redshifts / galaxies: general
© ESO, 2002
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