New constraints on lyman-α opacity with a sample of 62 quasars at z > 5.7

By S. Bosman, Xiaohui Fan, Linhua Jiang, S. Reed, Y. Matsuoka, George D. Becker, M. Haehnelt. 2018

135 citations recorded by the source corpus.

We present measurements of the mean and scatter of the intergalactic medium (IGM) Lyman-α opacity at 4.9 5.7, the largest sample assembled at these redshifts to date by a factor of two. The sample size enables us to sample cosmic variance at these redshifts more robustly than ever before. The spectra used here were obtained by the Sloan Digital Sky Survey, Dark Energy Survey–VISTA Hemisphere Survey, and Subaru High-z Exploration of Low-Luminosity Quasars collaborations, drawn from the Echellette Spectrograph and Imager and X-Shooter archives, reused from previous studies or observed specifically for this work. We measure the effective optical depth of Lyman-α in bins of 10, 30, 50, and 70 cMpc h−1, construct cumulative distribution functions under two treatments of upper limits on flux and explore an empirical analytic fit to residual Lyman-α transmission. We verify the consistency of our results with those of previous studies via bootstrap resampling and confirm the existence of tails towards high values in the opacity distributions, which may persist down to z ∼ 5.2. Comparing our results with predictions from cosmological simulations, we find further strong evidence against models that include a spatially uniform ionizing background and temperature–density relation. We also compare to IGM models that include either a fluctuating ultraviolet background dominated by rare quasars or temperature fluctuations due to patchy reionization. Although both models produce better agreement with the observations, neither fully captures the observed scatter in IGM opacity. Our sample of 62 z > 5.7 quasar spectra opens many avenues for future study of the reionization epoch.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/88d336028176814f5748860f73bb9543fff75592

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Citations in the corpus

Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “Finally, AGN may also provide a natural explanation for the large scatter in the Lyα opacity between different quasar sightlines close to redshift z = 6 (Becker et al. 2015; Bosman et al. 2018; Eilers et al. 2018).”
Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction (2019, background): “N 10 0.58551˙ ) was derived assuming that the ionizing background is uniform, while recent measurements imply that there are substantial spatial variations (e.g., Fan et al. 2006; Becker et al. 2015, 2018; Bosman et al. 2018).”
Large Ly α opacity fluctuations and low CMB τ in models of late reionization with large islands of neutral hydrogen extending to z < 5.5 (2018, methodology): “At z = 5–5.8, we compare our results with the measurements by Bosman et al. (2018) who present their results as ‘optimistic’ and ‘pessimistic’ limits on the distribution.”