CFHTLS weak-lensing constraints on the neutrino masses

TL;DR

The paper investigates how cosmic shear measurements from CFHTLS, when combined with CMB, BAO, and SN data, constrain the sum of neutrino masses under degenerate mass states. It develops a forward-modeling framework that includes massive neutrinos in the non-linear matter power spectrum and uses aperture-mass statistics to compare to data, employing both grid and importance-sampling likelihood analyses. The joint analysis yields a 95% confidence range of $0.03\,\mathrm{eV} < \sum m_\nu < 0.54\,\mathrm{eV}$ with a mean around $0.31\,\mathrm{eV}$, though the evidence for nonzero neutrino mass hinges on controlling systematics; when systematics are considered, the preference for massive neutrinos can disappear. The study highlights the sensitivity of neutrino constraints to cosmic-shear systematics and data combination choices, and it emphasizes the need for improved non-linear modeling and tomographic techniques in future surveys to achieve tighter, robust bounds.

Abstract

We use measurements of cosmic shear from CFHTLS, combined with WMAP-5 cosmic microwave background anisotropy data, baryonic acoustic oscillations from SDSS and 2dFGRS and supernovae data from SNLS and Gold-set, to constrain the neutrino mass. We obtain a 95% confidence level upper limit of 0.54 eV for the sum of the neutrino masses, and a lower limit of 0.03 eV. The preference for massive neutrinos vanishes when shear-measurement systematics are included in the analysis.

Figures (5)

• Figure 1: Left: Equation-of-state of fermionic massive particles as function of redshift $z$ for $m=1.0$ eV (solid line), 0.1 eV (dashed) and 0.01 eV (dotted). The transition redshift, Eq. (\ref{['eq:ztrans']}), is indicated in each case. The dashed-dotted curve shows the lensing efficiency window (arbitrary normalization). Right: Aperture-mass variance $\left<M^2_\mathrm{ap}( \theta )\right>$ with massive and massless neutrinos as function of angular scale. The massless neutrinos model (blue, thin lines) is shown in both linear and non-linear ( halofit) approximations. This indicates that the CFHTLS-T0003 data range (defined by the vertical lines) lies mostly in the non-linear regime, where the linear-approximation curve is much lower, and reaches the quasi-linear regime. Black, thick curves show three models of massive neutrinos (same masses and line types as in the left panel) with identical total mass densities ($\Omega_\mathrm{m}h^2=0.14$). The models for the two lighter neutrino cases are indistinguishable, while the case $m_\nu=1.0$ eV produces a significantly lower signal at small scales.
• Figure 2: Confidence contours (68% and 95%) from the aperture-mass dispersion between 1 and 230, for $\Omega_\nu=0$ (red, smaller) and marginalized over $\omega_\nu$ (blue, larger). Both cases are marginalized over the source redshift distribution and the remaining cosmological parameters.
• Figure 3: Left: Best-fit models found for massive ($m_\nu=0.53$ eV, $\Omega_\mathrm{m}=0.44$; dashed) and massless ($m_\nu=0$ eV, $\Omega_\mathrm{m}=0.30$; dotted) neutrino cases. Error bars are from CFHTLS-T0003. The models are extended beyond the data limit to illustrate the model separation at large scales. The normalized difference between the models is shown in the inset, where the horizontal line marks a 5% model-separation and the vertical line shows the data limit. Middle and Right: Confidence contours (68% and 95%) from the aperture-mass variance, in the $(\omega_\nu,\omega_\mathrm{cdm})$ and $(\omega_\nu,n_\mathrm{s})$ planes, marginalized over the hidden parameters.
• Figure 4: Joint analysis. Left and Middle: Contours at 95% C.L. of $(\omega_\nu,\omega_\mathrm{cdm})$ and $(\omega_\nu,n_\mathrm{s})$ for the four cases considered : WMAP5 alone (largest contour, red), WMAP5+CFHTLS (second largest, yellow), WMAP5+BAO+SNe (second smallest, green), WMAP5+BAO+SNe+CFHTLS (smallest contour, blue). Right: One-dimensional marginals for $\sum m_\nu$ showing the 95% C.L with vertical lines, for the same four cases : WMAP5 (dash-dot, red); WMAP5+CFHTLS (dash, pink) ; WMAP5+BAO+SNe (long dash, green); and WMAP5+BAO+SNe+CFHTLS (solid, blue). For the latter a lower bound was also found).
• Figure 5: Tests of the robustness of the result. Marginalized joint constraints (68% and 95% C.L.) obtained using the actual data (filled contours) and various assumptions (open contours). Left: Impact of systematics, assuming a 4% underestimation (solid) or marginalizing over a $\pm 25\%$ calibration bias (dashed). Middle and Right: Forecasts using a synthetic covariance matrix and the CFHTLS vector data (solid) or the same covariance matrix with a WMAP5 fiducial model (dashed).