Ly{\alpha} forest bounds on sterile neutrino production via neutrino self-interactions

TL;DR

This paper investigates sterile neutrino dark matter production via active neutrino self-interactions, analyzing its impact on structure formation and deriving stringent observational bounds using Lyα forest and CMB data.

Contribution

It introduces a self-consistent model of sterile neutrino production with active neutrino self-interactions and derives new constraints from Lyα forest and CMB observations.

Findings

Established the most stringent bounds on sterile neutrino DM to date.

Demonstrated the impact of active neutrino self-interactions on the matter power spectrum.

Provided constraints comparable to laboratory bounds.

Abstract

Sterile neutrinos in the keV mass range have long been considered a well-motivated dark matter (DM) candidate. In this work, we explore a sterile neutrino production mechanism through active neutrino self-interactions in the early universe, assuming that they constitute the full DM abundance. We implement a self-consistent treatment of the sterile-neutrino free streaming and the active-neutrino self-interactions on structure formation, which yield a unique scale-dependent modification to the linear matter power spectrum. We then set bounds on this scenario using a combination of the cosmic microwave background and Ly$\alpha$ forest constraints. Specifically, we utilize the two recent likelihoods derived from eBOSS data: (i) an effective field theory (EFT) based full-shape likelihood and (ii) a compressed likelihood obtained from the PRIYA-simulation emulator. We produce some of the most stringent observational constraints to date on sterile neutrino DM, comparable to the bounds from the most stringent laboratory constraints.