Measuring the Density Fields around Bright Quasars at $z\sim 6$ with XQR-30 Spectra

Abstract

Measuring the density of the intergalactic medium using quasar sightlines in the epoch of reionization is challenging due to the saturation of Lyman-$\alpha$ absorption. Near a luminous quasar, however, the enhanced radiation creates a proximity zone observable in the quasar spectra where the Lyman-$\alpha$ absorption is not saturated. In this study, we use $10$ high-resolution ($R\gtrsim 10,000$) $z\sim 6$ 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 $\text{Cosmic Reionization on Computers}$ simulation, and find a good agreement between $1.5$ to $3$pMpc 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 ${\sigma }_8=0.6\pm 0.3$. The uncertainty is mainly due to the limited number of high-quality quasar sightlines currently available. Utilizing the more than $>200$ known quasars at $z\gtrsim 6$, this method will allow us in the future to tighten the constraint on ${\sigma }_8$ to the percent level. In the region closer to the quasar within $1.5$ pMpc, we find the density is higher than predicted in the simulation by $1.23\pm 0.17$, suggesting the typical host dark matter halo mass of a bright quasar ($M_{1450}<-26.5$) at $z\sim 6$ is ${\log }_{10}(M/M_{\odot })=12.5_{-0.7}^{+0.4}$.

16 pages, 11 figures, submitted to ApJ, comments are welcome

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Cited by in corpus (11)

• XQR-30: the ultimate XSHOOTER quasar sample at the reionization epoch
• Examining the Decline in the C IV Content of the Universe over 4.3 < z < 6.3 using the E-XQR-30 Sample
• New quasar proximity zone size measurements at $z\sim 6$ using the enlarged XQR-30 sample
• New Radio-Loud QSOs at the end of the Re-ionisation Epoch
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• A Generative Model for Quasar Spectra
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• Galaxy Formation and Symbiotic Evolution with the Inter-Galactic Medium in the Age of ELT-ANDES
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• A first look at quasar-galaxy clustering at $z\simeq 7.3$
• Reconstructing Large-scale Temperature Profiles around $z\sim 6$ Quasars