Constraining cosmology with pairwise velocity estimator

¹ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL UK
e-mail: mayinzhe@manchester.ac.uk
² Astrophysics and Cosmology Research Unit, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, 4001, South Africa
³ Changchun Observatory, National Astronomical Observatories, CAS, Changchun, Jilin 130117, PR China
⁴ College of Physics, Jilin University, Changchun 130012, PR China
⁵ Center for High Energy Physics, Peking University, Beijing 100871, PR China

Received: 8 March 2015
Accepted: 3 August 2015

Abstract

In this paper, we develop a full statistical method for the pairwise velocity estimator previously proposed, and apply Cosmicflows-2  catalogue to this method to constrain cosmology. We first calculate the covariance matrix for line-of-sight velocities for a given catalogue, and then simulate the mock full-sky surveys from it, and then calculate the variance for the pairwise velocity field. By applying the 8315 independent galaxy samples and compressed 5224 group samples from Cosmicflows-2  catalogue to this statistical method, we find that the joint constraint on Ω_m^0.6h and σ₈ is completely consistent with the WMAP 9-year and Planck 2015 best-fitting cosmology. Currently, there is no evidence for the modified gravity models or any dynamic dark energy models from this practice, and the error-bars need to be reduced in order to provide any concrete evidence against/to support ΛCDM cosmology.