Growth history and quasar bias evolution at z < 3 from Quaia

Abstract

Abstract We make use of the Gaia - unWISE quasar catalogue, Quaia , to constrain the growth history out to high redshifts from the clustering of quasars and their cross-correlation with maps of the Cosmic Microwave Background (CMB) lensing convergence. Considering three tomographic bins, centred at redshifts z̅ i = [0.69, 1.59, 2.72], we reconstruct the evolution of the amplitude of matter fluctuations σ 8 ( z ) over the last ∼ 12 billion years of cosmic history. In particular, we make one of the highest-redshift measurements of σ 8 ( σ 8 ( z = 2.72) = 0.22 ± 0.06), finding it to be in good agreement (at the ∼ 1 σ level) with the value predicted by ΛCDM using CMB data from Planck . We also used the data to study the evolution of the linear quasar bias for this sample, finding values similar to those of other quasar samples, although with a less steep evolution at high redshifts. Finally, we study the potential impact of foreground contamination in the CMB lensing maps and, although we find evidence of contamination in cross-correlations at z ∼ 1.7 we are not able to clearly pinpoint its origin as being Galactic or extragalactic. Nevertheless, we determine that the impact of this contamination on our results is negligible.