Astroparticle Constraints from Cosmic Reionization and Primordial Galaxy Formation

We derive astroparticle constraints in different dark matter scenarios alternative to cold dark matter (CDM): thermal relic warm dark matter, WDM; fuzzy dark matter, $ψ$DM; self-interacting dark matter, SIDM; sterile neutrino dark matter, $ν$DM. Our framework is based on updated determinations of the high-redshift UV luminosity functions for primordial galaxies out to redshift $z\sim 10$, on redshift-dependent halo mass functions in the above DM scenarios from numerical simulations, and on robust constraints on the reionization history of the Universe from recent astrophysical and cosmological datasets. First, we build up an empirical model of cosmic reionization characterized by two parameters, namely the escape fraction $f_{\rm esc}$ of ionizing photons from primordial galaxies, and the limiting UV magnitude $M_{\rm UV}^{\rm lim}$ down to which the extrapolated UV luminosity functions are steeply increasing. Second, we perform standard abundance matching of the UV luminosity function and the halo mass function, obtaining a relationship between UV luminosity and halo mass whose shape depends on an astroparticle quantity $X$ specific of each DM scenario (e.g., WDM particle mass); we exploit such a relation to introduce in the analysis a constraint from primordial galaxy formation, in terms of the threshold halo mass above which primordial galaxies can efficiently form stars. Third, we implement a sequential updating Bayesian MCMC technique to perform joint inference on the three parameters $f_{\rm esc}$, $M_{\rm UV}^{\rm lim}$, $X$, and to compare the outcomes of different DM scenarios on the reionization history. Finally, we highlight the relevance of our astroparticle estimates in predicting the behavior of the high-redshift UV luminosity function at faint, yet unexplored magnitudes, that may be tested with the advent of the James Webb Space Telescope.

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