The VIMOS Public Extragalactic Redshift Survey (VIPERS)

Abstract

We carry out a joint analysis of redshift-space distortions and galaxy-galaxy lensing, with the aim of measuring the growth rate of structure; this is a key quantity for understanding the nature of gravity on cosmological scales and late-time cosmic acceleration. We make use of the final VIPERS redshift survey dataset, which maps a portion of the Universe at a redshift of z ≃ 0.8, and the lensing data from the CFHTLenS survey over the same area of the sky. We build a consistent theoretical model that combines non-linear galaxy biasing and redshift-space distortion models, and confront it with observations. The two probes are combined in a Bayesian maximum likelihood analysis to determine the growth rate of structure at two redshifts z = 0.6 and z = 0.86. We obtain measurements of f σ 8 (0.6) = 0.48 ± 0.12 and f σ 8 (0.86) = 0.48 ± 0.10. The additional galaxy-galaxy lensing constraint alleviates galaxy bias and σ 8 degeneracies, providing direct measurements of f and σ 8 : [ f (0.6), σ 8 (0.6)] = [0.93 ± 0.22,0.52 ± 0.06] and [ f (0.86), σ 8 (0.86)] = [0.99 ± 0.19,0.48 ± 0.04]. These measurements are statistically consistent with a Universe where the gravitational interactions can be described by General Relativity, although they are not yet accurate enough to rule out some commonly considered alternatives. Finally, as a complementary test we measure the gravitational slip parameter, E G, for the first time at z 0.6. We find values of E ̅ G (0.6) = 0.16±0.09 and E ̅ G (0.86) = 0.09±0.07, when E G is averaged over scales above 3 h -1 Mpc. We find that our E G measurements exhibit slightly lower values than expected for standard relativistic gravity in a ΛCDM background, although the results are consistent within 1−2 σ.