# Cosmological constraints on sterile neutrino Dark Matter production mechanisms

## TL;DR

This study uses cosmological data to constrain sterile neutrino production mechanisms, finding that sterile neutrinos likely constitute a fraction of dark matter and are consistent with X-ray and Ly-alpha observations.

## Contribution

It provides new constraints on sterile neutrino mass and fraction for both resonant production and scalar decay production mechanisms using combined cosmological datasets.

## Key findings

- Sterile neutrino mass and fraction are constrained within specific ranges.
- Results are consistent with X-ray and Ly-alpha forest upper limits.
- Sterile neutrinos are not the sole component of dark matter in these models.

## Abstract

We place constraints on sterile neutrino resonant production (RP) and scalar decay production (SDP) mechanisms assuming that sterile neutrino represents a fraction from the total Cold Dark Matter energy density. For the cosmological analysis, we complement the CMB anisotropies measurements with CMB lensing gravitational potential measurements, that are sensitive to the DM distribution out to high redshifts and with the cosmic shear data, that constraints the gravitational potential at lower redshifts than CMB. We show that our datasets have enough sensitivity to constrain the sterile neutrino mass and mass fraction inside the co-moving free-streaming horizon in both RP and SDP scenarios. For RP case we find that the best fit values of sterile neutrino mass and mixing angle are in the parameter space of interest for sterile neutrino DM decay interpretation of the 3.5 keV X-ray line with a DM mass fraction f_S=0.28 \pm 0.3 (at 68% CL) that excludes the assumption of sterile neutrinos as being all of the DM. For SDP case we find f_S=0.86 \pm 0.07 (at 68% CL), in agreement with the upper limit constraint on f_S from the X-ray non-detection and Ly-alpha forest measurements. The sterile neutrino mass predicted by both RP and SDP models are consistent within 0.3 \sigma.