http://arxiv.org/abs/1706.05205
We present the first simultaneous analysis of the galaxy overdensity and peculiar velocity fields by modelling their cross-covariance. We apply our new maximum-likelihood approach to data from the 6-degree Field Galaxy Survey (6dFGS), which has the largest single collection of peculiar velocities to date. We present a full derivation of the analytic expression for the cross-covariance between the galaxy overdensity and peculiar velocity fields and find direct evidence for a non-zero correlation between the fields on scales up to $\sim$50\mpch. When utilising the cross-covariance, our measurement of the normalised growth rate of structure is $f\sigma_8(z=0) = 0.424^{+0.067}{-0.064}$ (15% precision), and our measurement of the redshift-space distortion parameter is $\beta=0.341^{+0.062}{-0.058}$ (18% precision). Both measurements improve by $\sim$20\% compared to only using the auto-covariance information. This is consistent with the literature on multiple-tracer approaches, as well as Fisher matrix forecasts and previous analyses of 6dFGS. Our measurement of $f\sigma_8$ is consistent with the standard cosmological model, and we discuss how our approach can be extended to test alternative models of gravity.
C. Adams and C. Blake
Mon, 19 Jun 17
44/48
Comments: 20 pages, 10 figures, 3 tables, accepted for publication in MNRAS