摘要
The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large surveys can constrain the formation and evolution of structures and the cosmological parameters. On scales outside a few virial radii, the halo bias, b, is linear and the lensing signal is dominated by the correlated distribution of matter around galaxy clusters. We discuss a method to measure the power spectrum amplitude sigma(8) and b based on a minimal modelling. We considered a sample of similar to 120 000 clusters photometrically selected from the Sloan Digital Sky Survey in the redshift range 0.1 < z < 0.6. The autocorrelation was studied through the two-point function of a subsample of similar to 70 000 clusters; the matter-halo correlation was derived from the weak lensing signal of the subsample of similar to 1200 clusters with Canada-France-Hawaii Telescope Lensing Survey data. We obtained a direct measurement of b, which increases with mass in agreement with predictions of the Lambda cold dark matter paradigm. Assuming Omega(M) = 0.3, we found sigma(8) = 0.79 +/- 0.16. We used the same clusters for measuring both lensing and clustering and the estimate of sigma(8) did require neither the mass-richness relation, nor the knowledge of the selection function, nor the modelling of b. With an additional theoretical prior on the bias, we obtained sigma(8) = 0.75 +/- 0.08.
- 出版日期2015-6-1