Sensitivity tests of cosmic velocity fields to massive neutrinos

TL;DR

This study uses high-resolution simulations to analyze how massive neutrinos influence cosmic velocity fields, revealing that vorticity and divergence spectra are highly sensitive to neutrino mass, aiding in neutrino mass detection.

Contribution

First analysis of massive neutrino effects on various cosmic velocity components using collisionless hydrodynamics in high-resolution simulations.

Findings

Vorticity power spectrum is highly sensitive to neutrino mass.

Null hypothesis of massless neutrinos rejected at high significance.

Velocity field measurements can help determine neutrino mass and hierarchy.

Abstract

We investigate impacts of massive neutrinos on the cosmic velocity fields, employing high-resolution cosmological $N$-body simulations provided by the information-optimized CUBE code, where cosmic neutrinos are evolved using collisionless hydrodynamics and their perturbations can be accurately resolved. In this study we focus, for the first time, on the analysis of massive-neutrino induced suppression effects in various cosmic velocity field components of velocity magnitude, divergence, vorticity and dispersion. By varying the neutrino mass sum $M_\nu$ from 0 -- 0.4 eV, the simulations show that, the power spectra of vorticity -- exclusively sourced by non-linear structure formation that is affected by massive neutrinos significantly -- is very sensitive to the mass sum, which potentially provide novel signatures in detecting massive neutrinos. Furthermore, using the chi-square statistic, we quantitatively test the sensitivity of the density and velocity power spectra to the neutrino mass sum. Indeed, we find that, the vorticity spectrum has the highest sensitivity, and the null hypothesis of massless neutrinos is incompatible with both vorticity and divergence spectra from $M_\nu=0.1$ eV at high significance ($p$-value $= 0.03$ and $0.07$, respectively). These results demonstrate clearly the importance of peculiar velocity field measurements, in particular of vorticity and divergence components, in determination of neutrino mass and mass hierarchy.