Neutrino mass from cosmology: Impact of high-accuracy measurement of the Hubble constant
Abstract
Non-zero neutrino mass would affect the evolution of the Universe in observable ways, and a strong constraint on the mass can be achieved using combinations of cosmological data sets. We focus on the power spectrum of cosmic microwave background (CMB) anisotropies, the Hubble constant H0, and the length scale for baryon acoustic oscillations (BAO) to investigate the constraint on the neutrino mass, mnu. We analyze data from multiple existing CMB studies (WMAP5, ACBAR, CBI, BOOMERANG, and QUAD), recent measurement of H0 (SHOES), with about two times lower uncertainty (5%) than previous estimates, and recent treatments of BAO from the Sloan Digital Sky Survey (SDSS). We obtained an upper limit of mnu < 0.2eV (95% C.L.), for a flat LambdaCDM model. This is a 40% reduction in the limit derived from previous H0 estimates and one-third lower than can be achieved with extant CMB and BAO data. We also analyze the impact of smaller uncertainty on measurements of H0 as may be anticipated in the near term, in combination with CMB data from the Planck mission, and BAO data from the SDSS/BOSS program. We demonstrate the possibility of a 5 sigma detection for a fiducial neutrino mass of 0.1eV or a 95% upper limit of 0.04eV for a fiducial of mnu = 0eV. These constraints are about 50% better than those achieved without external constraint. We further investigate the impact on modeling where the dark-energy equation of state is constant but not necessarily -1, or where a non-flat universe is allowed. In these cases, the next-generation accuracies of Planck, BOSS, and 1% measurement of H0 would all be required to obtain the limit mnu < 0.05 - 0.06eV (95% C.L.) for the fiducial of mnu = 0eV. The independence of systematics argues for pursuit of both BAO and H0 measurements.