Neutrino Mass and Dark Energy from Weak Lensing

TL;DR

Focusing on the radial information contained in a future deep 4000 deg(2) survey, it is found that the expected (1-sigma) error on a neutrino mass is 0.1 eV, if the dark-energy parameters are allowed to vary.

Abstract

Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the universe. This distribution, and its evolution at late times, is sensitive to both the dark energy, a negative pressure energy density component, and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000 square degree survey, we find that the expected (1-sigma) error on a neutrino mass is 0.1 eV, if the dark energy parameters are allowed to vary. The constraints on dark energy parameters are similarly restrictive, with errors on w of 0.09. Much of the restrictive power on the dark energy comes not from the evolution of the gravitational potential but rather from how distances vary as a function of redshift in different cosmologies.

Figures (4)

• Figure 1: Top panel. Growth function vs. redshift for different choices of cosmological parameters. The base model in both panels (dark solid curve) has $\Omega_{\rm DE}=0.65, w=-1$ and $f_\nu=0.005$. Negative changes in the parameters are indicated by dashed curves. Bottom panel. Projection kernel as a function of redshift for background galaxies at redshift $z'=2$. The projection is completely independent of neutrino mass. Weak lensing convergence is the convolution of the two panels.
• Figure 2: Errors from a $4000$ deg$^2$ survey with one hundred galaxies per square arcminute with (inner region) and without (outer region) projection effects. Here the neutrino mass has been fixed. The outer region uses only information from the growth function; this information is much less constraining than including the combination of projection.
• Figure 3: Projected errors (all $1$-$\sigma$) on the dark energy density, equation of state, and neutrino mass from $4000$ square degree weak lensing survey. In each case, the innermost region is the constraint arising from fixing the parameter not shown (e.g., neutrino mass in the upper panel), while the outermost constraint comes from marginalizing over the third parameter. The middle region in the top panel emerges if the laboratory constraint on the neutrino mass is $0.1$ eV.
• Figure 4: Masses of the three neutrino species as a function of the lightest neutrino mass in a hierarchical mass scheme bb. At large $m_1$, all three must be nearly degenerate to account for the solar and atmospheric oscillations. The projected cosmological upper limit excludes the shaded region at $95\%$ CL.