Improved Constraints on the Neutral Intergalactic Hydrogen Surrounding Quasars at Redshiftsz> 6

We analyze the evolution of HII regions around the seven known SDSS quasarsat z>6. The comparison between observed and model radii of the HII regionsgenerated by these quasars individually, suggests that the surroundingintergalactic hydrogen is significantly neutral. When all constraints arecombined, the existing quasar sample implies a volume averaged neutral fractionthat is larger than 10% at z>6. This limited sample permits a preliminaryanalysis of the correlations between the quasar parameters, the sizes of theirHII regions, and the associated constraints on the neutral hydrogen fraction.We find no evidence in these correlations to contradict the interpretation thatthe red side of the Gunn-Peterson trough corresponds to the boundary between anHII region and a partially neutral IGM.Comment: 9 pages, 4 figures. Submitted to Ap