Constraining cosmology with pairwise velocity estimator
  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 $\Omega^{0.6}_{\rm
m}h$ and $\sigma_{8}$ 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 $\Lambda$CDM cosmology.
