%0 Generic %1 becker2014evidence %A Becker, George D. %A Bolton, James S. %A Madau, Piero %A Pettini, Max %A Ryan-Weber, Emma V. %A Venemans, Bram P. %D 2014 %K high-z hydrogen patchy reionization %T Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six %U http://arxiv.org/abs/1407.4850 %X We report the discovery of an extremely long ($\sim$110 Mpc/$h$) and dark ($\tau_eff 7$) Ly$\alpha$ trough extending down to $z 5.5$ towards the $z_em 6.0$ quasar ULAS J0148+0600. We use these new data in combination with Ly$\alpha$ forest measurements from 42 quasars at $4.5 z_em 6.4$ to conduct an updated analysis of the line-of-sight variance in the intergalactic Ly$\alpha$ opacity over $4 z 6$. We find that the scatter in transmission among lines of sight near $z 6$ significantly exceeds theoretical expectations for either a uniform ultraviolet background (UVB) or simple fluctuating UVB models in which the mean free path to ionizing photons is spatially invariant. The data, particularly near $z 5.6$-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor three or more beyond those expected from density variations alone. We argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. Even by $z 5.6$, however, a large fraction of the data is consistent with a uniform UVB, and by $z 5$ the data are fully consistent with opacity fluctuations arising solely from the density field. This suggests that while reionization may be ongoing at $z 6$, it has fully completed by $z \sim 5$.

@misc{becker2014evidence, abstract = {We report the discovery of an extremely long ($\sim$110 Mpc/$h$) and dark ($\tau_{\rm eff} \gtrsim 7$) Ly$\alpha$ trough extending down to $z \simeq 5.5$ towards the $z_{\rm em} \simeq 6.0$ quasar ULAS J0148+0600. We use these new data in combination with Ly$\alpha$ forest measurements from 42 quasars at $4.5 \le z_{\rm em} \le 6.4$ to conduct an updated analysis of the line-of-sight variance in the intergalactic Ly$\alpha$ opacity over $4 \le z \le 6$. We find that the scatter in transmission among lines of sight near $z \sim 6$ significantly exceeds theoretical expectations for either a uniform ultraviolet background (UVB) or simple fluctuating UVB models in which the mean free path to ionizing photons is spatially invariant. The data, particularly near $z \simeq 5.6$-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor three or more beyond those expected from density variations alone. We argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. Even by $z \simeq 5.6$, however, a large fraction of the data is consistent with a uniform UVB, and by $z \sim 5$ the data are fully consistent with opacity fluctuations arising solely from the density field. This suggests that while reionization may be ongoing at $z \sim 6$, it has fully completed by $z \sim 5$.}, added-at = {2014-07-21T09:28:52.000+0200}, author = {Becker, George D. and Bolton, James S. and Madau, Piero and Pettini, Max and Ryan-Weber, Emma V. and Venemans, Bram P.}, biburl = {https://www.bibsonomy.org/bibtex/29bdf73c6229221cd7e74826fe31b8944/miki}, description = {[1407.4850] Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six}, interhash = {448113eee157875358cd7e4a5dd1ce98}, intrahash = {9bdf73c6229221cd7e74826fe31b8944}, keywords = {high-z hydrogen patchy reionization}, note = {cite arxiv:1407.4850Comment: 19 pages, 20 figures, submitted to MNRAS, comments welcome}, timestamp = {2014-07-21T09:28:52.000+0200}, title = {Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six}, url = {http://arxiv.org/abs/1407.4850}, year = 2014 }