Peculiar Hubble Flows in Our Local Universe

Abstract

A formalism that simultaneously searches for the monopolar and dipolar peculiar velocities is presented. The formalism is applied to (1) the Mark III catalogue, (2) Lauer and Postman's Abell cluster catalogue, and (3) Riess et al.'s Type Ia supernova sample. The emphasis is drawn to the monopolar peculiar velocities, i.e., peculiar Hubble flows, within these samples. The samples show inconsistent peculiar Hubble flows within a depth of $\sim 60h^{-1}$ Mpc. Beyond a depth of $\sim 80h^{-1}$ Mpc, the Hubble flows of all samples converge to the global Hubble flow to better than 10% at the $2\sigma$ level. The results are compared with theoretical predictions. They at face value disfavor models predicting smaller peculiar velocities such as the tilted Cold Dark Matter model. Limitations of the catalogues are discussed, so are ways to improve the catalogues so that an accurate map of Hubble flows in our local universe can be drawn and be compared with theoretical predictions.