Late universe decaying dark matter can relieve the H_0 tension

Abstract

We study the cosmological effects of two-body dark matter decays where the products of the decay include a massless and a massive particle. We show that if the massive daughter particle is slightly warm it is possible to relieve the tension between distance ladder measurements of the present day Hubble parameter with measurements from the cosmic microwave background.

Figures (3)

• Figure 1: Results of the MCMC analysis of the decaying dark matter scenario with energy fraction $\epsilon$ and decay time $\tau$ using the late universe data together with effective data points between z=3 and 1090. The Hubble parameter $h$ and matter density $\Omega_{\mathrm{DM}}$ represent the values used in the $\Lambda$CDM universe that sets the initial conditions for the decaying dark matter model and not the values obtained in the latter (see text for details).
• Figure 2: The evolution of the Hubble parameter as a function of redshift for $\Lambda$CDM (thin grey line) and the proposed decaying dark matter scenario. Thick red line depicts the median while the red shaded area represents the $68\%$ allowed interval. The units of the y-axis are $\rm{km}\rm{s}^{-1}\rm{Mpc}^{-1}$. The decaying dark matter scenario proposed here can ease the tension between Planck18 2018arXiv180706209P and the SHOES measurement of $H_0$2018ApJ...861..126R while matching Planck18 $\Lambda$CDM universe at high redshifts.
• Figure 3: Left: The evolution of the equation of state $w_2$ of the massive daughter particle as a function of redshift. The shaded area represents the 68 percentile region. Right: Ratio of the difference for the linear growth factor between the decaying dark matter scenario proposed here and $\Lambda$CDM. Future surveys such as the Dark Energy Spectroscopic Instrument (DESI) 2016arXiv161100036D will be able to test the proposed decaying dark matter model. At lower redshifts DESI will constrain the growth factor with the Bright Galaxy Survey (BGS), around $z\approx 1$ , with the Main Survey (MS) and at higher redshifts with the Lyman $\alpha$ survey (Ly-$\alpha$) 2016arXiv161100036D.