Dark matter component decaying after recombination: Sensitivity to BAO and RSD probes

TL;DR

This study investigates how a small fraction of dark matter decaying after recombination affects cosmological measurements, finding that BAO and RSD data favor the standard model but allow for a few percent decaying dark matter, improving fit to some data.

Contribution

It extends previous decaying dark matter models by incorporating recent BAO and RSD measurements to constrain the decay fraction.

Findings

BAO/RSD data prefer standard ΛCDM over decaying dark matter.

Upper limit on decaying dark matter fraction is about 5%.

A small decaying dark matter component slightly improves data fit.

Abstract

It has been recently suggested~\cite{Berezhiani:2015yta} that a subdominant fraction of dark matter decaying after recombination may alleviate tension between high-redshift (CMB anisotropy) and low-redshift (Hubble constant, cluster counts) measurements. In this report, we continue our previous study~\cite{Chudaykin:2016yfk} of the decaying dark matter (DDM) model adding all available recent baryon acoustic oscillation (BAO) and redshift space distortions (RSD) measurements. We find, that the BAO/RSD measurements generically prefer the standard $\Lambda$CDM and combined with other cosmological measurements impose an upper limit on the DDM fraction at the level of $\sim$\,5\,\%, strengthening by a factor of 1.5 limits obtained in \cite{Chudaykin:2016yfk} mostly from CMB data. However, the numbers vary from one analysis to other based on the same Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) galaxy sample. Overall, the model with a few percent DDM fraction provides a better fit to the combined cosmological data as compared to the $\Lambda$CDM: the cluster counting and direct measurements of the Hubble parameter are responsible for that. The improvement can be as large as 1.5\,$\sigma$ and grows to 3.3\,$\sigma$ when the CMB lensing power amplitude ${\rm A_L}$ is introduced as a free fitting parameter.