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 $z \sim
5$.
Description
[1407.4850] Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
%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
}