Relic neutrino clustering in the Milky Way

TL;DR

This paper reviews how relic neutrinos, predicted by cosmology and affected by neutrino mass, can cluster in the Milky Way's gravitational potential, impacting detection efforts like PTOLEMY.

Contribution

It provides a detailed calculation of relic neutrino overdensity in the Milky Way and discusses implications for detection experiments.

Findings

Relic neutrinos can be gravitationally trapped in the Milky Way.

Overdensity of relic neutrinos affects detection prospects.

Implications for experiments like PTOLEMY.

Abstract

The Standard Cosmological Model predicts the existence of relic neutrinos, which are indirectly probed through the effective number of relativistic species in the early Universe. In addition, from neutrino flavour oscillations we know that at least two of the neutrino mass states have a non-zero mass. Since the expansion of the Universe has diluted the energy of relic neutrinos, those that are massive are also non relativistic today. This means that they can be trapped in strong gravitational potentials, such as the one of the Milky Way. We review the calculation of the local overdensity of relic neutrinos produced from the gravitational attraction of our Galaxy, Andromeda and the Virgo cluster, commenting on the implications for an experiment aiming at relic neutrino detection, such as the PTOLEMY project.