Exploring resonantly produced mixed sterile neutrino dark matter models

TL;DR

This paper investigates mixed sterile neutrino dark matter models, focusing on their production mechanisms, spectral properties, and implications for galaxy substructure, to explain the 3.55 keV X-ray line.

Contribution

It introduces a detailed analysis of mixed sterile neutrino models considering active-sterile mixing and lepton numbers, assessing their viability for dark matter and galaxy formation.

Findings

Sterile neutrino spectra are sensitive to active-sterile mixing parameters.

Models can produce spectra consistent with observed X-ray line.

Viability depends on subhalo formation estimates.

Abstract

An unidentified 3.55 keV X-ray line in stacked spectra of galaxies and clusters raises the interesting possibility that it originates from the decay of sterile neutrino dark matter. In this work, we explore mixed sterile neutrino dark matter models that combine cold dark matter and warmer sterile neutrino dark matter produced through lepton number-driven active-to-sterile neutrino transformation. We analyze the sensitivity of the sterile neutrino spectra on active-sterile mixing and on initial neutrino lepton numbers. Furthermore, we assess the viability of these models with estimates of the number of subhalos formed as the host sites of satellite galaxies.