Constraining sterile neutrino cosmologies with strong gravitational lensing observations at redshift z~0.2

TL;DR

This study uses gravitational lensing observations to constrain sterile neutrino dark matter models, providing bounds on their properties that are less affected by baryonic processes and thermal history assumptions.

Contribution

It offers new constraints on sterile neutrino dark matter using strong gravitational lensing data, complementing existing methods and reducing uncertainties related to baryonic effects.

Findings

Half-mode mass constrained to log M_hm < 12.0 M_sun

Sterile neutrino models with m_s < 0.8 keV are excluded

Constraints are less tight but more robust than other methods

Abstract

We use the observed amount of subhaloes and line-of-sight dark matter haloes in a sample of 11 gravitational lens systems from the Sloan Lens ACS Survey to constrain the free-streaming properties of the dark matter particles. In particular, we combine the detection of a small-mass dark matter halo by Vegetti et al. 2010 with the non-detections by Vegetti et al. 2014 and compare the derived subhalo and halo mass functions with expectations from cold dark matter (CDM) and resonantly produced sterile neutrino models. We constrain the half-mode mass, i.e. the mass scale at which the linear matter power spectrum is reduced by 50 per cent relatively to the CDM model, to be $\log M_{\rm{hm}} \left[M_\odot\right] < 12.0$ (equivalent thermal relic mass $m_{\rm th} > 0.3$ keV) at the 2$\sigma$ level. This excludes sterile neutrino models with neutrino masses $m_{\rm s} < 0.8$ keV at any value of $L_{\rm 6}$. Our constraints are weaker than currently provided by the number of Milky Way satellites, observations of the 3.5 keV X-ray line, and the Lyman $\alpha$ forest. However, they are more robust than the former as they are less affected by baryonic processes. Moreover, unlike the latter, they are not affected by assumptions on the thermal histories for the intergalactic medium. Gravitational lens systems with higher data quality and higher source and lens redshift are required to obtain tighter constraints.