Speaker
Description
Recent and upcoming CMB experiments are opening a new window onto the late-time Universe by reaching arcminute-scale resolution. These improvements allow us to extract information from CMB secondary anisotropies, which probe the evolution and distribution of structure over most of cosmic history. I will present new constraints on the amplitude of matter fluctuations over a broad redshift range, obtained by combining CMB lensing observations from ACT DR6 and Planck PR4 with quasars from the Quaia catalogue. By analysing the CMB lensing and quasar overdensity auto-correlations together with their cross-correlation, we are able to put a 12% constraint on the amplitude of matter fluctuations at redshift z~5; which constitutes one of the highest redshift measurements of structure growth to date.