Can sterile neutrinos be ruled out as warm dark matter candidates?

TL;DR

Adding constraints based on x-ray fluxes from the Andromeda galaxy, it is found that dark matter particles cannot be sterile neutrinos, unless they are produced by a nonstandard mechanism (resonant oscillations, coupling with the inflation) or get diluted by a large entropy release.

Abstract

We present constraints on the mass of warm dark matter (WDM) particles from a combined analysis of the matter power spectrum inferred from the Sloan Digital Sky Survey \lya flux power spectrum at 2.2<z<4.2, cosmic microwave background data, and the galaxy power spectrum. We obtain a lower limit of m~10 keV (2 sigma) if the WDM consists of sterile neutrinos and m~2 keV (2 sigma) for early decoupled thermal relics. If we combine this bound with the constraint derived from x-ray flux observations in the Coma cluster, we find that the allowed sterile neutrino mass is ~10 keV (in the standard production scenario). Adding constraints based on x-ray fluxes from the Andromeda galaxy, we find that dark matter particles cannot be sterile neutrinos, unless they are produced by a nonstandard mechanism (resonant oscillations, coupling with the inflaton) or get diluted by some large entropy release.

Figures (3)

• Figure 1: 2-dimensional marginalized likelihoods (68% and 95% confidence limits) for $n_s,\sigma_8,\Omega_{\rm m}$ and the effective optical depth at $z=3$, using the SDSS data at $z\le 4.2$ (left, green), $z\le 3.6$ (middle, white) and $z\le 3.2$ (right, blue).
• Figure 2: 1-dimensional marginalized likelihoods for the parameter $(1~\mathrm{keV})/m_{\rm s}$ for the SDSS Lyman-$\alpha$ data for the redshift ranges $z\le 3.2,3.6,3.8,4.2$ and the VHS Viel:2004bf data.
• Figure 3: This plot summarizes some of the parameter space constraints (at the 95% C.L.) for the sterile neutrino models, assuming that they constitute the dark matter. Limits are explained in the text.