CFHT UM2025 - Presentation Details
Abstract Details
Title: Measuring the Density Fields around Bright Quasars at z~6 with XQR-30 Spectra
Presenter: Huanqing Chen
Abstract:
Measuring the density of the intergalactic medium using quasar sightlines in the epoch of reionization is challenging due to the saturation of Lyman-α absorption. Near a luminous quasar, however, the enhanced radiation creates a proximity zone observable in the quasar spectra where the Lyman-α absorption is not saturated. In this study, we use 10 high-resolution (R≳10,000) z∼6 quasar spectra from the extended XQR-30 sample to measure the density field in the quasar proximity zones. We find a variety of environments within 3 pMpc distance from the quasars. We compare the observed density cumulative distribution function (CDF) with models from the Cosmic Reionization on Computers simulation, and find a good agreement between 1.5 to 3pMpc from the quasar. This region is far away from the quasar hosts and hence approaching the mean density of the universe, which allows us to use the CDF to set constraints on the cosmological parameter σ8=0.6±0.3. The uncertainty is mainl! y due to the limited number of high-quality quasar sightlines currently available. Utilizing the more than >200 known quasars at z≳6, this method will allow us in the future to tighten the constraint on σ8 to the percent level. In the region within 1.5 pMpc from the quasar, we find the density is higher than predicted in the simulation by 1.23±0.17, suggesting the typical host dark matter halo mass of a bright quasar (M1450<−26.5) at z∼6 is log10(M/M⊙)=12.5 0.4−0.7.