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2016ApJ...818...90M - Astrophys. J., 818, 90 (2016/February-2)

Constraining the warm dark matter particle mass through ultra-deep UV luminosity functions at z=2.


Abstract (from CDS):

We compute the mass function of galactic dark matter halos for different values of the warm dark matter (WDM) particle mass mX and compare it with the number density of ultra-faint galaxies derived from the deepest UV luminosity function available so far at redshift z ≈ 2. The magnitude limit MUV= -13 reached by such observations allows us to probe the WDM mass functions down to scales close to or smaller than the half-mass mode mass scale ∼109 M. This allowed for an efficient discrimination among predictions for different mXwhich turn out to be in practice independent of the star formation efficiency η adopted to associate the observed UV luminosities of galaxies to the corresponding dark matter halo masses. Adopting a conservative approach to take into account the existing theoretical uncertainties in the galaxy halo mass function, we obtain a robust limit mX≥ 1.8 keV for the mass of thermal relic WDM particles when comparing with the measured abundance of the faintest galaxies, while mX≥ 1.5 keV is obtained when we compare with the Schechter fit to the observed luminosity function. The corresponding lower limit for sterile neutrinos depends on the modeling of the production mechanism; for instance msterile≳ 4 keV holds for the Shi-Fuller mechanism. We discuss the impact of observational uncertainties on the above bound on mX. In the cold dark matter (CDM) limit mx ≫ 1 keV we recover the generic CDM result that very inefficient star formation efficiency is required to match the observed galaxy abundances. As a baseline for comparison with forthcoming observational results from the Hubble Space Telescope Frontier Field project, we provide predictions for the number density of faint galaxies with MUV= -13 for different values of the WDM particle mass and of the star formation efficiency η, which are valid up to z ≈ 4.

Abstract Copyright:

Journal keyword(s): dark matter - galaxies: abundances - galaxies: evolution - galaxies: formation

Status at CDS:  

Simbad objects: 3

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