Wyithe, J. Stuart B.Loeb, AbrahamCarilli, Chris2019-09-242005Wyithe, J. Stuart B., Abraham Loeb, and Chris Carilli. 2005. “Improved Constraints on the Neutral Intergalactic Hydrogen Surrounding Quasars at Redshiftsz> 6.” The Astrophysical Journal 628 (2): 575–82. https://doi.org/10.1086/430874.0004-637X1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:41393437We analyze the evolution of H II regions around the seven known SDSS quasars at z > 6. The comparison between the observed and model radii of the H II regions generated by these quasars individually suggests that the surrounding intergalactic hydrogen is significantly neutral. When all constraints are combined, the existing quasar sample implies a volume-averaged neutral fraction that is larger than 10% at z > 6. This limited sample permits a preliminary analysis of the correlations between the quasar parameters, the sizes of their H II regions, and the associated constraints on the neutral hydrogen fraction. We find no evidence in these correlations to contradict the interpretation that the red side of the Gunn-Peterson trough corresponds to the boundary between an H II region and a partially neutral IGM.en-USJournal Article2019-09-2410.1086/430874