Neutrino Halos in Clusters of Galaxies and their Weak Lensing Signature

TL;DR

This paper investigates whether the gravitational effects of relic neutrinos on galaxy cluster structures can be detected through weak lensing, highlighting the challenges in modeling and measurement accuracy.

Contribution

It provides a model of relic neutrino density profiles in galaxy clusters and assesses their potential weak lensing signatures and detectability.

Findings

Relic neutrinos slightly extend the outer mass profile of clusters.

Detection of neutrino effects requires extremely precise modeling and systematic error control.

Current observational and modeling challenges hinder practical detection of neutrino perturbations.

Abstract

We study whether non-linear gravitational effects of relic neutrinos on the development of clustering and large-scale structure may be observable by weak gravitational lensing. We compute the density profile of relic massive neutrinos in a spherical model of a cluster of galaxies, for several neutrino mass schemes and cluster masses. Relic neutrinos add a small perturbation to the mass profile, making it more extended in the outer parts. In principle, this non-linear neutrino perturbation is detectable in an all-sky weak lensing survey such as EUCLID by averaging the shear profile of a large fraction of the visible massive clusters in the universe, or from its signature in the general weak lensing power spectrum or its cross-spectrum with galaxies. However, correctly modeling the distribution of mass in baryons and cold dark matter and suppressing any systematic errors to the accuracy required for detecting this neutrino perturbation is severely challenging.