Resonant Sterile Neutrino Dark Matter in the Local and High-z Universe

TL;DR

This study compares different sterile neutrino dark matter models through simulations of the Local Group and the universe, finding that nonlinear structures are insensitive to initial power spectrum differences, but linear regime differences could be tested observationally.

Contribution

It provides a detailed comparison of resonant and thermal sterile neutrino models using simulations, highlighting their effects on structure formation and potential observational tests.

Findings

Nonlinear regime properties are insensitive to initial power spectrum differences.

Differences in the linear matter power spectrum persist at higher redshifts.

Future observations of dwarf satellites could rule out some sterile neutrino models.

Abstract

Sterile neutrinos comprise an entire class of dark matter models that, depending on their production mechanism, can be hot, warm, or cold dark matter. We simulate the Local Group and representative volumes of the Universe in a variety of sterile neutrino models, all of which are consistent with the possible existence of a radiative decay line at ~3.5 keV. We compare models of production via resonances in the presence of a lepton asymmetry (suggested by Shi & Fuller 1999) to "thermal" models. We find that properties in the highly nonlinear regime - e.g., counts of satellites and internal properties of halos and subhalos - are insensitive to the precise fall-off in power with wavenumber, indicating that nonlinear evolution essentially washes away differences in the initial (linear) matter power spectrum. In the quasi-linear regime at higher redshifts, however, quantitative differences in the 3D matter power spectra remain, raising the possibility that such models can be tested with future observations of the Lyman-alpha forest. While many of the sterile neutrino models largely eliminate multiple small-scale issues within the Cold Dark Matter (CDM) paradigm, we show that these models may be ruled out in the near future via discoveries of additional dwarf satellites in the Local Group.