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Issue A&A Volume 368, Number 3, March IV 2001 Page(s) L17 - L20 Section Letters DOI 10.1051/0004-6361:20010161

A&A 368, L17-L20 (2001)
DOI: 10.1051/0004-6361:20010161

On the quiescence of the Hubble flow in the vicinity of the Local Group

A study using galaxies with distances from the Cepheid PL-relation

T. Ekholm^{1, 2}, Yu. Baryshev³, P. Teerikorpi², M. O. Hanski² and G. Paturel<sup>1

1</sup>  CRAL -Observatoire de Lyon, 69561 Saint Genis Laval Cedex, France
²  Tuorla Observatory, 21500 Piikkiö, Finland
³  Astronomical Institute, St. Petersburg State University, Staryj Petergoff, 198504, St. Petersburg, Russia

(Received 8 December 2000 / Accepted 31 January 2001)

Abstract
Cepheid distances of local galaxies (<7 Mpc) are used to study the very nearby velocity field, as pioneered by Sandage (1986) who also pointed out its remarkable properties: linearity and quietness. The new data show that the velocity dispersion in the distance range as seen from the barycentre of the Local Group 1-8 Mpc is as low as 38 km s^-1. The local rate of expansion coincides with the global Hubble constant. Down to 1.5 Mpc we cannot detect a deviation from the linear Hubble flow. This puts an upper limit for the mass of the Local Group, for a wide class of Friedman models, including those with the cosmological constant.

Key words: cosmology: observations -- galaxies: distances and redshifts -- galaxies: general -- galaxies: kinematics and dynamics -- Local Group

Offprint request: T. Ekholm, timo@typhon.univ-lyon1.fr

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