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

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 amplitude of mass fluctuations. 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 Sloan Digital Sky Survey (SDSS) galaxies to determine their halo mass probability distribution. We use these halo mass probability distributions to predict the bias for each luminosity subsample. Galaxies below L_* are antibiased with b<1 and for these galaxies bias is only weakly dependent on luminosity. In contrast, for galaxies above L_* bias is rapidly increasing with luminosity. These observations are in an excellent agreement with theoretical predictions based on weak lensing halo mass determination combined with halo bias-mass relations. We find that for standard cosmological parameters theoretical predictions are able to explain the observed luminosity dependence of bias over six magnitudes in absolute luminosity. We combine the bias constraints with those from the Wilkinson Microwave Anisotropy Probe (WMAP) and the SDSS power spectrum analysis to derive new constraints on bias and σ₈. For the most general parameter space that includes running and neutrino mass, we find σ₈=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 three degenerate families from m_ν<0.6 eV without bias to m_ν<0.18 eV with bias (95% C.L.), which is weakened to m_ν<0.24 eV if running is allowed. The corresponding limit for 3 massless+1 massive neutrino is 1.37 eV.