Tomographic constraints on gravity from angular redshift fluctuations in the late Universe
Abstract
Fluctuations in sky maps of galaxy redshifts, dubbed angular redshift fluctuations (ARF), contain precise information about the growth rate of structures and the nature of gravity in the Universe. Specifically, ARFs constrain the combination of cosmological parameters $H/H_0\, f\sigma _8(z)$ , while being an intrinsically tomographic probe and largely insensitive to many observational systematic errors, all without requiring the assumption of any redshifttodistance relation under a given fiducial cosmology. We present the first cosmological constraints derived from ARF by using Baryon Oscillation Spectroscopic Survey (BOSS) LOWZ(Low redshift(Z))+CMASS(Constant MASS) DR12(Data Release 12) galaxy samples, obtaining 7 per cent accurate constraints on H/H_{0}fσ_{8}(z) at more than 20 redshifts over the range z ∈ [0.26, 0.72]. Our bestfitting value is $10{{\ \rm per\ cent}}$ larger, but compatible at the 1.4σ level, than the ΛCDM expectation set by Planck observations of cosmic microwave background (CMB) radiation. Our tomographic measurements, combined with these CMB data, provide one of the strongest constraints on the gravity index γ, $\gamma =0.44^{+0.09}_{0.07}$ , which lies within 2σ of the prediction of General Relativity (γ_{GR} ≃ 0.55).
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 2021
 DOI:
 10.1093/mnrasl/slab021
 arXiv:
 arXiv:2005.06568
 Bibcode:
 2021MNRAS.503L..62H
 Keywords:

 gravitation;
 cosmological parameters;
 largescale structure of the Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 5 pages, 3 figures, matches accepted version in MNRAS letters