Using peculiar velocity surveys to constrain neutrino masses
  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 $\textit{do}$ contain information on the sum of the masses of neutrinos
$\sum m_{\nu}$, 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 $\textit{Planck}$ measurements of the Cosmic Microwave
Background. Compared to the full constraining power offered by
$\textit{Planck}$ and higher redshift DESI/Euclid data, we find that the
benefit of including peculiar velocities only marginally improves neutrino mass
constraints. However, when one is limited to modeling only quasi-linear scales,
adds additional degrees of freedom via a varying number of effective neutrino
species ($N_{\text{eff}}$), or does not include information from
$\textit{Planck}$, 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 $\sum m_{\nu}$
($\sigma_{\sum m_{\nu}} = 0.051$ eV; 68% confidence limit) comparable to those
from $\textit{Planck}$, from spectroscopic galaxy surveys alone, as long as the
peculiar velocity data is available. This could allow for an independent
comparison between constraints on $\sum m_{\nu}$ from the early- and late-time
Universe probes that are particularly timely given current cosmological
parameter tensions.
