Large‐scale streaming of flat galaxies

Abstract

AbstractWe consider a sample of thin edge‐on galaxies from new a Flat Galaxy Catalogue, FGC (Karachentsev et al. 1993) covering the whole sky. The galaxies have been selected into the Catalogue by their apparent axis ratio a/b > 7 and angular diameter a ≥ 0.6 arcmin. Among 4455 such galaxies 893 have estimates both radial velocity and inner motion amplitude, however most part of them (542) are concetrated in the Arecibo zone. This sample is characterized by the medians: uh = +5300 Km s−1, W50 = 285 km s−1 and Ty = Scd.To determine distances and peculiar velocities of the flat galaxies we use different modifications of the Tully‐Fisher relation between linear diameter and HI linewidth taking into account also their surface brightness. A typical scatter of galaxy distance estimates by this method corresponds to dex (0.09).In a dipole approach we calculated the terms of bulk motion of the galaxies. Relative to the CMB frame the population of FGC galaxies is moving to apex l = 319° ± 10°, b = +28° ± 11° with velocity 260 ± 40 km s−1. Here the formal 1σ errors correspond to a scattering of estimates carried out with different kinds of the TF relation (blue or red diameters, two‐ or three‐parametric regressions).A consecutive removing of nearby galaxies by a condition of V < Vmin leads to a rise of the mean bulk velocity and to a drift of the apex direction: Vbulk = 400 ± 70km s−1, l = 304° ± 6°, b = +23° ± 12° for Vmin = 3500km s−1 and Vbulk = 450 ± 40km s−1, l = 301° ± 7°, b = +23° ± 4° for Vmin = 8500km s−1, what remains not far from the Shapley concentration (l = 311°, b = +30°) of rich clusters.