Arbitrating the S8 discrepancy with growth rate measurements from redshift-space distortions
Jun 2, 2021
13 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 505 (2021) 4, 5427-5437
- Published: Jul 8, 2021
e-Print:
- 2106.01208 [astro-ph.CO]
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Abstract: (Oxford University Press)
Within the Lambda cold dark matter (ΛCDM) model, measurements from recent cosmic microwave background (CMB) and weak lensing (WL) surveys have uncovered a ∼3σ disagreement in the inferred value of the parameter ||, quantifying the amplitude of late-time matter fluctuations. Before questioning whether the S_8 discrepancy calls for new physics, it is important to assess the view of measurements other than CMB and WL ones on the discrepancy. Here, we examine the role of measurements of the growth rate f(z) in arbitrating the S_8 discrepancy, considering measurements of fσ_8(z) from redshift-space distortions (RSDs). Our baseline analysis combines RSD measurements with geometrical measurements from baryon acoustic oscillations (BAO) and Type Ia Supernovae (SNeIa), given the key role of the latter in constraining Ω_m. From this combination and within the ΛCDM model, we find ||, and quantify the agreement between RSD + BAO + SNeIa and Planck to be at the 2.2σ level: the mild disagreement is therefore compatible with a statistical fluctuation. We discuss combinations of RSD measurements with other data sets, including the statistic. This combination increases the discrepancy with Planck, but we deem it significantly less robust. Our earlier results are stable against an extension where we allow the dark energy equation of state w to vary. We conclude that, from the point of view of combined growth rate and geometrical measurements, there are hints, but no strong evidence yet, for the Planck ΛCDM cosmology overpredicting the amplitude of matter fluctuations at redshifts z ≲ 1. From this perspective, it might therefore still be premature to claim the need for new physics from the S_8 discrepancy.Note:
- 13 pages, 1 table, 3 figures. Accepted for publication in MNRAS
- cosmological parameters
- dark energy
- dark matter
References(199)
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