Cross-correlations of the Cosmic Neutrino Background: HR-DEMNUni simulation analysis

TL;DR

This paper uses high-resolution simulations to analyze cross-correlations of the Cosmic Neutrino Background with other cosmological signals, revealing non-zero correlations at large scales that could be detectable and informative about neutrino properties.

Contribution

It provides the first detailed theoretical prediction of cross-correlation signals involving the cosmic neutrino background, highlighting their potential for early detection and cosmological insights.

Findings

Cross-correlations are non-zero at large scales.

Cross-correlations are less affected by cosmic variance.

Predicted signals can reveal neutrino mass effects.

Abstract

We use the high-resolution HR-DEMNUni simulations to compute cross-correlations of the Cosmic Neutrino Background quantities, like neutrino density, deflection angle, and velocity, with other quantities, like cold dark matter density and effective weak lensing convergence, by accounting for the space-time delay between signals on Earth. We provide this to theoretically illustrate how much can be learned from these cross-correlation signals, once the cosmic neutrino background is detected with instruments in multiple locations. Against a naive expectation of null cross-correlation, we show that the signal is non zero, specially at the largest scales. We also discuss the scenario of co-located cross-correlations between dark matter, weak lensing and a future neutrino-induced photon emission signal. As cross-correlations will be comparable to auto-correlations of the cosmic neutrino background itself and are less affected by cosmic variance and shotnoise, these might be the ones to be measured first. Our predictions thus provide the imprint of what cosmological massive neutrinos, with total mass $\sum{m_\nu} \sim 0.1$ eV, should look like from cosmological observations.