Observations suggest that CII was more abundant than CIV in the intergalactic
medium towards the end of the hydrogen reionisation epoch. This transition
provides a unique opportunity to study the enrichment history of intergalactic
gas and the growth of the ionising background (UVB) at early times. We study
how carbon absorption evolves from z=10-5 using a cosmological hydrodynamic
simulation that includes a self-consistent multifrequency UVB as well as a
well-constrained model for galactic outflows to disperse metals. Our predicted
UVB is within 2-4 times that of Haardt & Madau (2012), which is fair agreement
given the uncertainties. Nonetheless, we use a calibration in post-processing
to account for Lyman-alpha forest measurements while preserving the predicted
spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way
that it always exceeds the volume average in regions where metals are found.
This implies both that a spatially-uniform UVB is a poor approximation and that
metal absorption is not sensitive to the epoch when HII regions overlap
globally even at column densites of 10^12 cm^-2. We find, consistent with
observations, that the CII mass fraction drops to low redshift while CIV rises
owing the combined effects of a growing UVB and continued addition of carbon in
low-density regions. This is mimicked in absorption statistics, which broadly
agree with observations at z=6-3 while predicting that the absorber column
density distributions rise steeply to the lowest observable columns. Our model
reproduces the large observed scatter in the number of low-ionisation absorbers
per sightline, implying that the scatter does not indicate a partially-neutral
Universe at z=6.
%0 Generic
%1 finlator2014reionisation
%A Finlator, K.
%A Thompson, R.
%A Huang, S.
%A Davé, R.
%A Zackrisson, E.
%A Oppenheimer, B. D.
%D 2014
%K carbon reionisation simulation
%T The Reionisation of Carbon
%U http://arxiv.org/abs/1412.4810
%X Observations suggest that CII was more abundant than CIV in the intergalactic
medium towards the end of the hydrogen reionisation epoch. This transition
provides a unique opportunity to study the enrichment history of intergalactic
gas and the growth of the ionising background (UVB) at early times. We study
how carbon absorption evolves from z=10-5 using a cosmological hydrodynamic
simulation that includes a self-consistent multifrequency UVB as well as a
well-constrained model for galactic outflows to disperse metals. Our predicted
UVB is within 2-4 times that of Haardt & Madau (2012), which is fair agreement
given the uncertainties. Nonetheless, we use a calibration in post-processing
to account for Lyman-alpha forest measurements while preserving the predicted
spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way
that it always exceeds the volume average in regions where metals are found.
This implies both that a spatially-uniform UVB is a poor approximation and that
metal absorption is not sensitive to the epoch when HII regions overlap
globally even at column densites of 10^12 cm^-2. We find, consistent with
observations, that the CII mass fraction drops to low redshift while CIV rises
owing the combined effects of a growing UVB and continued addition of carbon in
low-density regions. This is mimicked in absorption statistics, which broadly
agree with observations at z=6-3 while predicting that the absorber column
density distributions rise steeply to the lowest observable columns. Our model
reproduces the large observed scatter in the number of low-ionisation absorbers
per sightline, implying that the scatter does not indicate a partially-neutral
Universe at z=6.
@misc{finlator2014reionisation,
abstract = {Observations suggest that CII was more abundant than CIV in the intergalactic
medium towards the end of the hydrogen reionisation epoch. This transition
provides a unique opportunity to study the enrichment history of intergalactic
gas and the growth of the ionising background (UVB) at early times. We study
how carbon absorption evolves from z=10-5 using a cosmological hydrodynamic
simulation that includes a self-consistent multifrequency UVB as well as a
well-constrained model for galactic outflows to disperse metals. Our predicted
UVB is within 2-4 times that of Haardt & Madau (2012), which is fair agreement
given the uncertainties. Nonetheless, we use a calibration in post-processing
to account for Lyman-alpha forest measurements while preserving the predicted
spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way
that it always exceeds the volume average in regions where metals are found.
This implies both that a spatially-uniform UVB is a poor approximation and that
metal absorption is not sensitive to the epoch when HII regions overlap
globally even at column densites of 10^{12} cm^{-2}. We find, consistent with
observations, that the CII mass fraction drops to low redshift while CIV rises
owing the combined effects of a growing UVB and continued addition of carbon in
low-density regions. This is mimicked in absorption statistics, which broadly
agree with observations at z=6-3 while predicting that the absorber column
density distributions rise steeply to the lowest observable columns. Our model
reproduces the large observed scatter in the number of low-ionisation absorbers
per sightline, implying that the scatter does not indicate a partially-neutral
Universe at z=6.},
added-at = {2014-12-17T09:29:31.000+0100},
author = {Finlator, K. and Thompson, R. and Huang, S. and Davé, R. and Zackrisson, E. and Oppenheimer, B. D.},
biburl = {https://www.bibsonomy.org/bibtex/2dabb4420e20a5260472cd3b3b4f6698b/miki},
description = {[1412.4810] The Reionisation of Carbon},
interhash = {8c0007a1b1eaa7342154fd6e2abce986},
intrahash = {dabb4420e20a5260472cd3b3b4f6698b},
keywords = {carbon reionisation simulation},
note = {cite arxiv:1412.4810Comment: 16 pages, 14 figures, accepted to MNRAS},
timestamp = {2014-12-17T09:29:31.000+0100},
title = {The Reionisation of Carbon},
url = {http://arxiv.org/abs/1412.4810},
year = 2014
}