How cold is Dark Matter? Constraints from Milky Way Satellites

TL;DR

This study uses high-resolution simulations and semi-analytic models to compare Cold and Warm Dark Matter scenarios, constraining dark matter particle mass based on Milky Way satellite observations.

Contribution

It demonstrates that warm dark matter particles with masses as low as 2 keV can reproduce observed satellite galaxy properties, suggesting a lower mass limit of 1 keV.

Findings

WDM models with 2-5 keV match satellite abundance.

Warm dark matter with 1 keV is consistent with observations.

Results align with constraints from Lyman-alpha forest and lensing.

Abstract

We test the luminosity function of Milky Way satellites as a constraint for the nature of Dark Matter particles. We perform dissipationless high-resolution N-body simulations of the evolution of Galaxy-sized halo in the standard Cold Dark Matter (CDM) model and in four Warm Dark Matter (WDM) scenarios, with a different choice for the WDM particle mass (m_w). We then combine the results of the numerical simulations with semi-analytic models for galaxy formation, to infer the properties of the satellite population. Quite surprisingly we find that even WDM models with relatively low m_w values (2-5 keV) are able to reproduce the observed abundance of ultra faint (Mv<-9) dwarf galaxies, as well as the observed relation between Luminosity and mass within 300 pc. Our results suggest a lower limit of 1 keV for thermal warm dark matter, in broad agreement with previous results from other astrophysical observations like Lyman-alpha forest and gravitational lensing.