paper

Observational constraints on cosmic neutrinos and dark energy revisited

arXiv:1210.2136 · doi:10.1088/1475-7516/2012/11/018

Abstract

Using several cosmological observations, i.e. the cosmic microwave background anisotropies (WMAP), the weak gravitational lensing (CFHTLS), the measurements of baryon acoustic oscillations (SDSS+WiggleZ), the most recent observational Hubble parameter data, the Union2.1 compilation of type Ia supernovae, and the HST prior, we impose constraints on the sum of neutrino masses ($\mnu$), the effective number of neutrino species ($\neff$) and dark energy equation of state (), individually and collectively. We find that a tight upper limit on $\mnu$ can be extracted from the full data combination, if $\neff$ and are fixed. However this upper bound is severely weakened if $\neff$ and are allowed to vary. This result naturally raises questions on the robustness of previous strict upper bounds on $\mnu$, ever reported in the literature. The best-fit values from our most generalized constraint read $\mnu=0.556^{+0.231}_{-0.288}\rm eV$, $\neff=3.839\pm0.452$, and at 68% confidence level, which shows a firm lower limit on total neutrino mass, favors an extra light degree of freedom, and supports the cosmological constant model. The current weak lensing data are already helpful in constraining cosmological model parameters for fixed . The dataset of Hubble parameter gains numerous advantages over supernovae when , particularly its illuminating power in constraining $\neff$. As long as is included as a free parameter, it is still the standardizable candles of type Ia supernovae that play the most dominant role in the parameter constraints.

arXiv comment39 pages, 15 figures, 7 tables, accepted to JCAP

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