Neutrino constraints from future nearly all-sky spectroscopic galaxy surveys

TL;DR

This work addresses whether future near-infrared galaxy surveys, when combined with Planck CMB priors, can detect the cosmic neutrino background and determine the absolute neutrino mass scale. It employs a Fisher-matrix forecast based on the redshift-space galaxy power spectrum $P_{obs}(k,\\mu)$, incorporating Alcock-Paczynski distortions, redshift uncertainties, and a redshift-dependent transfer function $T(k,z)$ that encodes massive neutrino free-streaming. Two survey strategies are analyzed: slitless (Euclid-like) H-alpha surveys and multi-slit (SPACE/JEDI/WFIRST) magnitude-limited surveys, each with distinct redshift ranges and biases. The results indicate that, with Planck priors, 1-sigma errors on $M_{\\nu}$ can reach ~0.03–0.05 eV and on $N_{eff}$ about ~0.08, enabling a high-significance (>3 sigma) detection for $M_{\\nu} pprox 0.1$ eV and robust constraints across hierarchies; overall, these near-IR galaxy surveys could detect the cosmic neutrino background and constrain the neutrino mass scale, complementing particle-physics experiments.

Abstract

We examine whether future, nearly all-sky galaxy redshift surveys, in combination with CMB priors, will be able to detect the signature of the cosmic neutrino background and determine the absolute neutrino mass scale. We also consider what constraints can be imposed on the effective number of neutrino species. In particular we consider two spectroscopic strategies in the near-IR, the so-called "slitless" and "multi-slit" approaches, whose examples are given by future space-based galaxy surveys, as EUCLID for the slitless case, or SPACE, JEDI, and possibly WFIRST in the future, for the multi-slit case. We find that, in combination with Planck, these galaxy probes will be able to detect at better than 3--sigma level and measure the mass of cosmic neutrinos: a) in a cosmology-independent way, if the sum of neutrino masses is above 0.1 eV; b) assuming spatial flatness and that dark energy is a cosmological constant, otherwise. We find that the sensitivity of such surveys is well suited to span the entire range of neutrino masses allowed by neutrino oscillation experiments, and to yield a clear detection of non-zero neutrino mass. The detection of the cosmic relic neutrino background with cosmological experiments will be a spectacular confirmation of our model for the early Universe and a window into one of the oldest relic components of our Universe.