Neutrino Signatures on the High Transmission Regions of the Lyman-alpha Forest

TL;DR

This paper demonstrates that analyzing high transmission regions in the Lyman-alpha forest can provide precise measurements of the total neutrino mass, complementing other cosmological probes.

Contribution

It introduces a novel method to estimate neutrino masses using the statistics of high transmissivity regions in the Lyman-alpha forest from hydrodynamic simulations.

Findings

Neutrino mass can be constrained to less than 0.4 eV with 200 quasar spectra.

Systematic errors do not eliminate the neutrino signal in the Lyman-alpha forest.

Combining this method with other cosmological data improves neutrino mass bounds.

Abstract

We quantify the impact of massive neutrinos on the statistics of low density regions in the intergalactic medium (IGM) as probed by the Lyman-alpha forest at redshifts z=2.2--4. Based on mock but realistic quasar (QSO) spectra extracted from hydrodynamic simulations with cold dark matter, baryons and neutrinos, we find that the probability distribution of weak Lyman-alpha absorption features, as sampled by Lyman-alpha flux regions at high transmissivity, is strongly affected by the presence of massive neutrinos. We show that systematic errors affecting the Lyman-alpha forest reduce but do not erase the neutrino signal. Using the Fisher matrix formalism, we conclude that the sum of the neutrino masses can be measured, using the method proposed in this paper, with a precision smaller than 0.4 eV using a catalog of 200 high resolution (S/N~100) QSO spectra. This number reduces to 0.27 eV by making use of reasonable priors in the other parameters that also affect the statistics of the high transitivity regions of the Lyman-alpha forest. The constraints obtained with this method can be combined with independent bounds from the CMB, large scale structures and measurements of the matter power spectrum from the Lyman-alpha forest to produce tighter upper limits on the sum of the masses of the neutrinos.