Anisotropy of the Galaxies Detected by IRAS

Abstract

We generate a catalogue of 6730 galaxies uniformly selected over most of the sky (> 9.5sr) using the IRAS point source catalogue. Our catalogue reveals a small (4–7%), but robust dipole anisotropy in the galaxy distribution that points towards l = 235°, b = 45°, within 30° of the microwave dipole anisotropy. Angular correlation analysis suggests that subsets of the catalogue have characteristic distances D* ≃50 – 100h^-1 Mpc. The good agreement in direction of these dipoles suggests that the IRAS galaxies roughly trace the large scale mass distribution, that the microwave dipole velocity is mostly induced by the local supercluster (cz < 3000 km s ^-1), and that the indicated cosmological density is high (Ω ≈ 0.5). A full sky redshift survey is in progress to obtain a more precise estimate.