Local velocity field from sosie galaxies - I. The Peebles' model

Pratton et al. (1997) showed that the velocity field around clusters could generate an apparent distortion that appears as tangential structures or radial filaments. In the present paper we determine the parameters of the Peebles' model (1976) describing infall of galaxies onto clusters with the aim of testing quantitatively the amplitude of this distortion. The distances are determined from the concept of sosie galaxies (Paturel 1984) using 21 calibrators for which the distances were recently calculated from two independent Cepheid calibrations. We use both B and I-band magnitudes. The Spaenhauer diagram method is used to correct for the Malmquist bias. We give the equations for the construction of this diagram. We analyze the apparent Hubble constant in different regions around Virgo and obtain simultaneously the Local Group infall and the unperturbed Hubble constant. We found: VLG-infall = 208 +/- 9 km s(-1) log H = 1.82 +/- 0.04 (H approximate to 66 +/- 6 km s(-1) Mpc(-1)). The front side and backside infalls can be seen around Virgo and Fornax. In the direction of Virgo the comparison is made with the Peebles' model. We obtain: v(infall) = C-Virgo/(r)0.9+/-0.2 with C-Virgo = 2800 for Virgo and C-Fornax = 1350 for Fornax, with the adopted units (km s(-1) and Mpc). We obtain the following mean distance moduli: mu(Virgo) = 31.3 +/- 0.2 (r = 18 Mpc) mu(Fornax) = 31.7 +/- 0.3 (r = 22 Mpc). All these quantities form an accurate and coherent system.