SDSS galaxy bias from halo mass-bias relation and its cosmological implications

Abstract

We combine the measurements of luminosity dependence of bias with the luminosity dependent weak lensing analysis of dark matter around galaxies to derive the galaxy bias and constrain nonlinear mass and cosmological parameters. We take advantage of theoretical and simulation predictions that predict that while halo bias is rapidly increasing with mass for high masses, it is nearly constant in low mass halos. We use a new weak lensing analysis around the same SDSS galaxies to determine their halo mass probability distribution. These halo mass probability distributions are used to predict the bias for each luminosity subsample and we find an excellent agreement with observed values. The required nonlinear mass suggests slightly lower matter density than usually assumed, Omegam=0.25+/- 0.03 for the simplest models. We combine the bias constraints with those from the WMAP and the SDSS power spectrum analysis to derive new constraints on bias and sigma_8. For the most general parameter space we find sigma_8=0.88+/- 0.06 and b_*=0.99+/- 0.07. In the context of spatially flat models we improve the limit on the neutrino mass for the case of 3 degenerate families from m_nu<0.6eV without bias to m_nu<0.18eV with bias (95% c.l.), which is weakened to m_nu<0.24eV if running is allowed. The corresponding limit for 3 massless + 1 massive neutrino is 1.37eV.