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DES Y1 results: Splitting growth and geometry to test ΛCDM

2020/10/31 by J. Muir, E. Baxter, V. Miranda +100
Physics and Astronomy · #astro-ph.CO

paper · pdf · doi:10.1103/physrevd.103.023528

published as Phys. Rev. D 103, 023528 (2021) · 35 pages, 18 figures. Updated to match published version

arxiv created 2021/01/28 · arxiv updated 2021/02/01

Abstract

We analyze Dark Energy Survey (DES) data to constrain a cosmological model where a subset of parameters -- focusing on Ωm -- are split into versions associated with structure growth (e.g. Ωm\rm grow) and expansion history (e.g. Ωm\rm geo). Once the parameters have been specified for the ΛCDM cosmological model, which includes general relativity as a theory of gravity, it uniquely predicts the evolution of both geometry (distances) and the growth of structure over cosmic time. Any inconsistency between measurements of geometry and growth could therefore indicate a breakdown of that model. Our growth-geometry split approach therefore serves as both a (largely) model-independent test for beyond-ΛCDM physics, and as a means to characterize how DES observables provide cosmological information. We analyze the same multi-probe DES data as arXiv:1811.02375 : DES Year 1 (Y1) galaxy clustering and weak lensing, which are sensitive to both growth and geometry, as well as Y1 BAO and Y3 supernovae, which probe geometry. We additionally include external geometric information from BOSS DR12 BAO and a compressed Planck 2015 likelihood, and external growth information from BOSS DR12 RSD. We find no significant disagreement with Ωm\rm grow=Ωm\rm geo. When DES and external data are analyzed separately, degeneracies with neutrino mass and intrinsic alignments limit our ability to measure Ωm\rm grow, but combining DES with external data allows us to constrain both growth and geometric quantities. We also consider a parameterization where we split both Ωm and w, but find that even our most constraining data combination is unable to separately constrain Ωm\rm grow and w\rm grow. Relative to ΛCDM, splitting growth and geometry weakens bounds on σ8 but does not alter constraints on h.

Citations