Measuring neutrino properties through the peculiar motion of galaxies

Neutrinos are believed to be the most abundant fermions in our Universe, but their masses are still one of the biggest puzzles in physics. As the presence of massive neutrinos affects both the cosmic expansion and the gravitational potential of structures, large-scale structures are expected to be a powerful probe to constrain neutrino properties in cosmology. Among these large-scale probes, the galaxy velocity field contains half of the phase space information, and the mean pairwise velocity is potentially a very useful observable to constrain structure formation. Using neutrino-involved N-body simulation, we study the dependences of the halo-halo pairwise velocities on the cosmic neutrino masses and chemical potentials. We found that the neutrino mass effect dominates over the chemical potential effect in these pairwise velocities, and the former always suppresses the structure formation. Finally, we make use of galaxy-galaxy pairwise velocity calculated from the observation (Cosmicflows-3) to constrain neutrino masses and chemical potentials.