Astronomy & Astrophysics

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A&A 389, 812-824 (2002)
DOI: 10.1051/0004-6361:20020649

The very local Hubble flow

I. D. Karachentsev¹, M. E. Sharina^{1, 2}, D. I. Makarov^{1, 2}, A. E. Dolphin³, E. K. Grebel⁴, D. Geisler⁵, P. Guhathakurta⁶, P. W. Hodge⁷, V. E. Karachentseva⁸, A. Sarajedini⁹ and P. Seitzer¹⁰

¹ 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

(Received 24 December 2001 / Accepted 25 April 2002)

Abstract
We present Hubble Space Telescope/WFPC2 images of eighteen galaxies situated in the vicinity of the Local Group (LG) as part of an ongoing snapshot survey of nearby galaxies. Their distances derived from the magnitude of the tip of the red giant branch are $1.92\pm0.10$ Mpc (ESO 294-010), $3.06\pm0.37$ (NGC 404), $3.15\pm0.32$ (UGCA 105), $1.36\pm0.07$ (Sex B), $1.33\pm0.08$ (NGC 3109), $2.64\pm0.21$ (UGC 6817), $2.86\pm0.14$ (KDG 90), $2.27\pm0.19$ (IC 3104), $2.54\pm0.17$ (UGC 7577), $2.56\pm0.15$ (UGC 8508), $3.01\pm0.29$ (UGC 8651), $2.61\pm0.16$ (KKH 86), $2.79\pm0.26$ (UGC 9240), $1.11\pm0.07$ (SagDIG), $0.94\pm0.04$ (DDO 210), $2.07\pm0.18$ (IC 5152), $2.23\pm0.15$ (UGCA 438), and $2.45\pm0.13$ (KKH 98). Based on the velocity-distance data for 36 nearest galaxies around the LG, we find the radius of the zero-velocity surface of the LG to be $R_0 = (0.94\pm0.10)$ Mpc, which yields a total mass $M_{\rm LG} = (1.3\pm0.3)\times 10^~M_{\odot}$ . The galaxy distribution around the LG reveals a Local Minivoid which does not contain any galaxy brighter than M_V=-11 mag within a volume of ~100 Mpc ³. The local Hubble flow seems to be very cold, having a one-dimensional mean random motion of ~30 km s ^-1. The best-fit value of the local Hubble parameter is $73\pm15$ km s ^-1 Mpc ^-1. The luminosity function for the nearby field galaxies is far less steep than one for members of the nearest groups.

Key words: galaxies: dwarf -- galaxies: distances and redshifts -- galaxies: kinematics and dynamics -- galaxies: Local Group

Offprint request: M. E. Sharina, sme@sao.ru

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