Using peculiar velocity surveys to constrain neutrino masses

Abstract

The presence of massive neutrinos in the early Universe is expected to have influenced the observed distribution of galaxies and their observed motions. In this work, we explore whether measurements of galaxy peculiar velocities could allow us to improve upon neutrino mass constraints from galaxy redshift surveys alone. Using Fisher matrix forecasts, we show that the galaxy peculiar motions do contain information on the sum of the masses of neutrinos σmν, and that this information can be used to improve upon constraints that may be obtained from low-redshift galaxy surveys (z < 0.5) combined with Planck measurements of the cosmic microwave background. Compared to the full constraining power offered by Planck and higher redshift DESI data, we find that the benefit of including peculiar velocities only marginally improves neutrino mass constraints. However, when one is limited to modelling only quasi-linear scales, adds additional degrees of freedom via a varying number of effective neutrino species (Neff), or does not include information from Planck, our results show that the inclusion of peculiar velocity measurements can still substantially improve upon the constraints. As such, we demonstrate that it may be possible to achieve upper bounds on σmν (σmν = 0.051 eV; 68 per cent confidence limit) comparable to those from Planck, from spectroscopic galaxy surveys alone, as long as the peculiar velocity data are available. This could allow for an independent comparison between constraints on σmν from the early- A nd late-time Universe probes that are particularly timely given current cosmological parameter tensions.