Constraining the warm dark matter particle mass through ultra-deep UV luminosity functions at z = 2
- INAF—Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone (Italy)
- Observatoire de Paris, LERMA, CNRS UMR 8112, 61, Observatoire de Paris PSL, Sorbonne Universités, UPMC Univ. Paris 6, 61 Avenue de l’Observatoire, F-75014 Paris (France)
We compute the mass function of galactic dark matter halos for different values of the warm dark matter (WDM) particle mass m{sub X} 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 M{sub UV} = −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 ∼10{sup 9} M{sub ⊙}. This allowed for an efficient discrimination among predictions for different m{sub X} which 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 m{sub X} ≥ 1.8 keV for the mass of thermal relic WDM particles when comparing with the measured abundance of the faintest galaxies, while m{sub X} ≥ 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 m{sub sterile} ≳ 4 keV holds for the Shi–Fuller mechanism. We discuss the impact of observational uncertainties on the above bound on m{sub X}. In the cold dark matter (CDM) limit m{sub X}≫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 M{sub UV} = −13 for different values of the WDM particle mass and of the star formation efficiency η, which are valid up to z ≈ 4.
- OSTI ID:
- 22887035
- Journal Information:
- Astrophysical Journal, Vol. 818, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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