The Imprint of Neutrinos on Clustering in Redshift Space

We investigate the signatures left by the cosmic neutrino background on the clustering of matter, CDM+baryons, and halos in redshift space using the HADES simulations. While on large scales the clustering of matter and CDM+baryons is very different in cosmologies with massive and massless neutrinos, we find that the effect neutrinos have on the clustering of CDM+baryons in redshift space on small scales is almost entirely due to the change in σ ₈. We show that the effect of neutrinos on the clustering of halos is very different, on all scales, from the effects induced by varying σ ₈. We find that the effects of neutrinos on the growth rate of CDM+baryons ranges from ∼0.3% to 2% on scales for neutrinos with masses . We compute the bias between the momentum of halos and the momentum of CDM+baryons and find it to be 1 on large scales for all models with massless and massive neutrinos considered. We show that, even on very large scales, nonlinear corrections are important to describe the clustering of halos in redshift space in cosmologies with massless and massive neutrinos at low redshift. We find that hydrodynamics and astrophysical processes, as implemented in our simulations, only distort the relative effect that neutrinos induce on the anisotropic clustering of matter, CDM+baryons, and halos in redshift space by less than 1%. Thus, the effect of neutrinos in the fully nonlinear regime can be written as a transfer function with very weak dependence on astrophysics that can be studied through N-body simulations.