Searching for modified gravity: scale and redshift dependent constraints from galaxy peculiar velocities

Johnson, Andrew, Blake, Chris, Dossett, Jason, Koda, Jun, Parkinson, David and Joudaki, Shahab (2016) Searching for modified gravity: scale and redshift dependent constraints from galaxy peculiar velocities. Monthly Notices of the Royal Astronomical Society, 458 3: 2725-2744. doi:10.1093/mnras/stw447

Author Johnson, Andrew
Blake, Chris
Dossett, Jason
Koda, Jun
Parkinson, David
Joudaki, Shahab
Title Searching for modified gravity: scale and redshift dependent constraints from galaxy peculiar velocities
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 1365-2966
Publication date 2016-05-21
Year available 2016
Sub-type Article (original research)
DOI 10.1093/mnras/stw447
Open Access Status Not yet assessed
Volume 458
Issue 3
Start page 2725
End page 2744
Total pages 20
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Collection year 2017
Language eng
Formatted abstract
We present measurements of both scale- and time-dependent deviations from the standard gravitational field equations. These late-time modifications are introduced separately for relativistic and non-relativistic particles, by way of the parameters Gmatter(k, z) and Glight(k, z) using two bins in both scale and time, with transition wavenumber 0.01 Mpc-1 and redshift 1. We emphasize the use of two dynamical probes to constrain this set of parameters, galaxy power-spectrum multipoles and the direct peculiar velocity power spectrum, which probe fluctuations on different scales. The multipole measurements are derived from the WiggleZ and Baryon Oscillation Spectroscopic Survey (BOSS) CMASS galaxy redshift surveys and the velocity power spectrum is measured from the velocity sub-sample of the 6-degree Field Galaxy Survey. We combine these measurements with additional cosmological probes. Using a Markov Chain Monte Carlo likelihood analysis, we find the inferred best-fitting parameter values of Gmatter(k, z) and Glight(k, z) to be consistent with the standard model at the 95 per cent confidence level. We expand this analysis by performing Bayesian model selection between our phenomenological model and general relativity. Using the evidence ratio we find 'no support' for including modifications to general relativity. Furthermore, accounting for the Alcock-Paczynski effect, we perform joint fits for the expansion history and growth index γ we measure γ = 0.665 ± 0.067 (68 per cent CL) for a fixed expansion history, and γ = 0.73 +0.08−0.10 (68 per cent CL) when the expansion history is allowed to deviate from Λ cold dark matter. For the latter case, we observe a 2σ tension with the standard model where γ = 0.554.
Keyword Cosmological parameters
Cosmology: Observations
Dark energy
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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