DESI and other dark energy experiments in the era of neutrino mass measurements

TL;DR

This paper provides comprehensive Fisher matrix projections for future cosmological measurements, emphasizing the importance of combining multiple surveys and including neutrino mass as a key parameter to improve dark energy and other cosmological constraints.

Contribution

It offers a consistent set of projections for various experiments, highlighting the impact of neutrino mass on dark energy measurements and the benefits of combining different observational data.

Findings

Neutrino mass can be measured to ~0.02 eV or better.

Broadband galaxy power improves dark energy constraints.

Combining lensing and redshift surveys yields significant gains.

Abstract

We present Fisher matrix projections for future cosmological parameter measurements, including neutrino masses, dark energy, curvature, modified gravity, the inflationary perturbation spectrum, non-Gaussianity, and dark radiation. We focus on DESI and generally redshift surveys (BOSS, HETDEX, eBOSS, Euclid, and WFIRST), but also include CMB (Planck) and weak gravitational lensing (DES and LSST) constraints. The goal is to present a consistent set of projections, for concrete experiments, which are otherwise scattered throughout many papers and proposals. We include neutrino mass as a free parameter in most projections, as it will inevitably be relevant -- DESI and other experiments can measure the sum of neutrino masses to ~0.02 eV or better, while the minimum possible sum is ~0.06 eV. We note that the BAO-only use of galaxy clustering is substantially degraded as a dark energy probe in the presence of neutrino mass uncertainty -- using broadband galaxy power is critical, especially pushing it to as small a scale as possible, and big gains are achieved by combining lensing survey constraints with redshift survey constraints. We do not try to be especially innovative, e.g., in careful treatments of potential systematic errors -- these projections are intended as a straightforward baseline for comparison to more detailed analyses.