A Stringent Limit on the Warm Dark Matter Particle Masses from the Abundance of z=6 Galaxies in the Hubble Frontier Fields

TL;DR

This study uses the abundance of ultra-faint galaxies at redshift 6 to set the most stringent limits to date on the mass of warm dark matter particles, independent of galaxy formation physics.

Contribution

It provides the tightest constraints on warm dark matter particle mass using galaxy abundance data, ruling out certain sterile neutrino production mechanisms.

Findings

WDM particle mass > 2.9 keV at 1-sigma confidence

Constraints exclude the Dodelson-Widrow sterile neutrino production

Sterile neutrino mass > 6.1 keV for Shi-Fuller mechanism

Abstract

We show that the recently measured UV luminosity functions of ultra-faint lensed galaxies at z= 6 in the Hubble Frontier Fields provide an unprecedented probe for the mass m_X of the Warm Dark Matter candidates independent of baryonic physics. Comparing the measured abundance of the faintest galaxies with the maximum number density of dark matter halos in WDM cosmologies sets a robust limit m_X> 2.9 keV for the mass of thermal relic WDM particles at a 1-sigma confidence level, m_X> 2.4 keV at 2-sigma, and m_X> 2.1 keV at 3-sigma. These constitute the tightest constraints on WDM particle mass derived to date independently of the baryonic physics involved in galaxy formation. We discuss the impact of our results on the production mechanism of sterile neutrinos. In particular, if sterile neutrinos are responsible for the 3.5 keV line reported in observations of X-ray clusters, our results firmly rule out the Dodelson-Widrow production mechanism, and yield m_{sterile}> 6.1 keV for sterile neutrinos produced via the Shi-Fuller mechanism.