New constraints on Lyman-α opacity using 92 quasar lines of sight

Sarah E.I. Bosman, Xiaohui Fan, Linhua Jiang, Sophie Reed, Yoshiki Matsuoka, George Becker, Alberto Rorai

Research output: Contribution to journalArticlepeer-review


The large scatter in Lyman-α opacity at z > 5.3 has been an ongoing mystery, prompting a flurry of numerical models. A uniform ultra-violet background has been ruled out at those redshifts, but it is unclear whether any proposed models produce sufficient inhomogeneities. In this paper we provide an update on the measurement which first highlighted the issue: Lyman-α effective optical depth along high-z quasar lines of sight. We nearly triple on the previous sample size in such a study thanks to the cooperation of the DES-VHS, SHELLQs, and SDSS collaborations as well as new reductions and spectra. We find that a uniform UVB model is ruled out at 5.1 < z < 5.3, as well as higher redshifts, which is perplexing. We provide the first such measurements at z ∼ 6. None of the numerical models we confronted to this data could reproduce the observed scatter.

Original languageEnglish (US)
Pages (from-to)234-237
Number of pages4
JournalProceedings of the International Astronomical Union
Issue numberS333
StatePublished - 2017


  • cosmology: observations
  • large-scale structure of universe
  • quasars: absorption lines

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


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