Precision cosmology with the 2MASS clustering dipole

TL;DR

This paper uses the extensive 2MASS galaxy catalog to precisely measure the Local Group's acceleration and estimate the cosmological parameter beta, improving the accuracy of clustering dipole analyses.

Contribution

It provides the most precise measurement of the beta parameter from the clustering dipole using 2MASS data, with two independent methods.

Findings

Beta estimated at ~0.4 with a few percent error

First precise determination of beta from 2MASS clustering dipole

Supports the use of all-sky galaxy surveys for cosmological parameter estimation

Abstract

Comparison of peculiar velocities of galaxies with their gravitational accelerations (induced by the density field) is one of the methods to constrain the redshift distortion parameter \beta=(\Omega_m^0.55)/b, where \Omega_m is the non-relativistic matter density parameter and b is the linear bias. In particular, one can use the motion of the Local Group (LG) for that purpose. Its peculiar velocity is known from the dipole component of the cosmic microwave background, whereas its acceleration can be estimated with the use of an all-sky galaxy catalog, from the so-called clustering dipole. At the moment, the biggest dataset of that kind is the Two Micron All Sky Survey Extended Source Catalog (2MASS XSC) containing almost 1 million galaxies and complete up to ~300 Mpc/h. We applied 2MASS data to measure LG acceleration and used two methods to estimate the beta parameter. Both of them yield \beta~0.4 with an error of several per cent, which is the most precise determination of this parameter from the clustering dipole to date.