ORCID Profile
0000-0003-2764-8248
Current Organisation
University of Nottingham
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Publisher: Oxford University Press (OUP)
Date: 15-03-2011
Publisher: Oxford University Press (OUP)
Date: 15-11-2010
Publisher: Oxford University Press (OUP)
Date: 19-12-2022
Abstract: We present the Sherwood–Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations that use a new lightweight hybrid scheme for treating radiative transfer effects. This scheme follows the spatial variations in the ionizing radiation field, as well as the associated fluctuations in IGM temperature and pressure smoothing. It is computationally much cheaper than full radiation hydrodynamics simulations, and circumvents the difficult task of calibrating a galaxy formation model to observational constraints on cosmic reionization. Using this hybrid technique, we study the spatial fluctuations in IGM properties that are seeded by patchy cosmic reionization. We investigate the relevant physical processes and assess their impact on the z & 4 Lyman-α forest. Our main findings are: (i) consistent with previous studies patchy reionization causes large-scale temperature fluctuations that persist well after the end of reionization, (ii) these increase the Lyman-α forest flux power spectrum on large scales, and (iii) result in a spatially varying pressure smoothing that correlates well with the local reionization redshift. (iv) Structures evaporated or puffed up by photoheating cause notable features in the Lyman-α forest, such as flat-bottom or double-dip absorption profiles.
Publisher: Oxford University Press (OUP)
Date: 30-06-2017
Abstract: We study the effect of different feedback prescriptions on the properties of the low-redshift (z ≤ 1.6) Lyα forest using a selection of hydrodynamical simulations drawn from the Sherwood simulation suite. The simulations incorporate stellar feedback, active galactic nuclei (AGN) feedback and a simplified scheme for efficiently modelling the low column density Lyα forest. We confirm a discrepancy remains between Cosmic Origins Spectrograph (COS) observations of the Lyα forest column density distribution function (CDDF) at z ≃ 0.1 for high column density systems ($N_{\\rm H\\,\\rm {\\small I}}& ^{14}\\rm \\,cm^{-2}$), as well as Lyα velocity widths that are too narrow compared to the COS data. Stellar or AGN feedback – as currently implemented in our simulations – has only a small effect on the CDDF and velocity width distribution. We conclude that resolving the discrepancy between the COS data and simulations requires an increase in the temperature of overdense gas with Δ = 4–40, either through additional He$\\,\\rm \\scriptstyle II\\,$photoheating at z & 2 or fine-tuned feedback that ejects overdense gas into the intergalactic medium at just the right temperature for it to still contribute significantly to the Lyα forest. Alternatively a larger, currently unresolved turbulent component to the line width could resolve the discrepancy.
Publisher: Oxford University Press (OUP)
Date: 22-01-2015
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S1743921316011467
Abstract: Observations of metal absorption lines in the spectra of QSOs out to z 6 are providing an important probe into the enrichment and ionization state of the intergalactic medium (IGM) at the tail end of reionization. Using simulations with four different feedback models, including the Illustris and Sherwood simulations, we investigate how the overall incidence rate and equivalent width distribution of metal-line absorbers varies with the galactic wind scheme. The low-ionization absorbers are reasonably insensitive to the feedback implementation, with all models reasonably close to the observed incidence rate of O i absorbers. However, all of our models struggle to reproduce the observations of C iv , which is probing overdensities close to the mean at z ~ 6, suggesting that the metals are not being transported out into the IGM efficiently enough in these simulations.
Publisher: Oxford University Press (OUP)
Date: 02-02-2011
Publisher: Oxford University Press (OUP)
Date: 07-09-2019
Abstract: We use state-of-the-art hydrodyamical simulations from the Sherwood, EAGLE, and Illustris projects to examine the signature of Mz = 0 ≃ 1014 M⊙ protoclusters observed in Ly α absorption at z ≃ 2.4. We find that there is a weak correlation between the mass overdensity, δm, and the Ly α effective optical depth relative to the mean, $\\delta _{\\tau _\\textrm{eff}}$, averaged over $15~h^{-1}\\, \\textrm{cMpc}$ scales, although scatter in the δm–$\\delta _{\\tau _\\textrm{eff}}$ plane means it is not possible to uniquely identify large-scale overdensities with strong Ly α absorption. Although all protoclusters are associated with large-scale mass overdensities, most sightlines through protoclusters in a ∼106$\\rm cMpc^{3}$ volume probe the low column density Ly α forest. A small subset of sightlines that pass through protoclusters exhibit coherent, strong Ly α absorption on $15h^{-1}\\rm \\, cMpc$ scales, although these correspond to a wide range in mass overdensity. Assuming perfect removal of contamination by Ly α absorbers with d ing wings, more than half of the remaining sightlines with $\\delta _{\\tau _{\\rm eff}}\\gt 3.5$ trace protoclusters. It is furthermore possible to identify a model-dependent $\\delta _{\\tau _{\\rm eff}}$ threshold that selects only protoclusters. However, such regions are rare: excluding absorption caused by d ed systems, less than 0.1 per cent of sightlines that pass through a protocluster have $\\delta _{\\tau _{\\rm eff}}\\gt 3.5$, meaning that any protocluster s le selected in this manner will also be highly incomplete. On the other hand, coherent regions of Ly α absorption also provide a promising route for identifying and studying filamentary environments at high redshift.
Publisher: American Astronomical Society
Date: 29-01-2015
Publisher: Oxford University Press (OUP)
Date: 31-03-2022
Abstract: We examine the column density distribution function (CDDF) and Doppler parameter distribution from hydrodynamical simulations and Cosmic Origins Spectrograph (COS) observations of the Ly α forest at redshift 0 ≤ z ≤ 0.2. Allowing for a factor of two uncertainty in the metagalactic H $\\, \\rm \\scriptstyle I \\, $ photoionization rate, our hydrodynamical simulations are in good agreement (1–1.5σ) with the shape and litude of the observed CDDF at H $\\, \\rm \\scriptstyle I \\, $ column densities $10^{13.3}\\rm \\, cm^{-2}\\le N_{\\rm H\\,{\\small I}}\\le 10^{14.5}\\rm \\, cm^{-2}$. However, the Doppler widths of the simulated lines remain too narrow with respect to the COS data. We argue that invoking AGN feedback does not resolve this discrepancy. We also disfavour enhanced photoheating rates as a potential solution, as this requires an unphysically hard UV background spectrum. If instead appealing to a non-canonical source of heating, an additional specific heat injection of $u \\lesssim 6.9\\rm \\, eV\\, m_{\\rm p}^{-1}$ is required at z ≲ 2.5 for gas that has $N_{\\rm H\\,{\\small I}}\\simeq 10^{13.5}\\rm \\, cm^{-2}$ by z = 0.1. Alternatively, there may be an unresolved line of sight turbulent velocity component of $v_{\\rm turb}\\lesssim 8.5\\rm \\, km\\, s^{-1}(N_{\\rm H\\,{\\small I}}/10^{13.5}\\rm \\, cm^{-2})^{0.21}$ for the coldest gas in the diffuse IGM.
Publisher: Oxford University Press (OUP)
Date: 24-03-2011
Publisher: Cambridge University Press (CUP)
Date: 03-2005
Publisher: Oxford University Press (OUP)
Date: 02-03-2023
Abstract: Inhomogeneous reionization enhances the 1D Ly α forest power spectrum on large scales at redshifts z ≥ 4. This is due to coherent fluctuations in the ionized hydrogen fraction that arise from large-scale variations in the post-reionization gas temperature, which fade as the gas cools. It is therefore possible to use these relic fluctuations to constrain inhomogeneous reionization with the power spectrum at wavenumbers $\\log _{10}(k/{\\rm km^{-1}\\, s})\\lesssim -1.5$. We use the Sherwood-Relics suite of hybrid radiation hydrodynamical simulations to perform a first analysis of new Ly α forest power spectrum measurements at 4.0 ≤ z ≤ 4.6. These data extend to wavenumbers $\\log _{10}(k/{\\rm km^{-1}\\, s})\\simeq -3$, with a relative uncertainty of 10–20 per cent in each wavenumber bin. Our analysis returns a 2.7σ preference for an enhancement in the Ly α forest power spectrum at large scales, in excess of that expected for a spatially uniform ultraviolet background. This large-scale enhancement could be a signature of inhomogeneous reionization, although the statistical precision of these data is not yet sufficient for obtaining a robust detection of the relic post-reionization fluctuations. We show that future power spectrum measurements with relative uncertainties of ≲ 2.5 per cent should provide unambiguous evidence for an enhancement in the power spectrum on large scales.
Publisher: Oxford University Press (OUP)
Date: 21-12-2007
Publisher: Oxford University Press (OUP)
Date: 11-03-2005
Publisher: Oxford University Press (OUP)
Date: 11-01-2017
Publisher: Oxford University Press (OUP)
Date: 18-05-2010
Publisher: Oxford University Press (OUP)
Date: 09-11-2012
DOI: 10.1093/MNRAS/STS156
Publisher: Oxford University Press (OUP)
Date: 03-2004
Publisher: Oxford University Press (OUP)
Date: 09-2023
Publisher: Oxford University Press (OUP)
Date: 14-12-2020
Abstract: We present a new, uniform analysis of the H i transmitted flux (F) and H i column density ($N_{\\mathrm{H\\,{\\small I}}}$) distribution in the low-density IGM as a function of redshift z for 0 & z & 3.6 using 55 HST/COS FUV (Δz = 7.2 at z & 0.5), five HST/STIS + COS NUV (Δz = 1.3 at z ∼ 1) and 24 VLT/UVES, and Keck/HIRES (Δz = 11.6 at 1.7 & z & 3.6) AGN spectra. We performed a consistent, uniform Voigt profile analysis to combine spectra taken with different instruments, to reduce systematics and to remove metal-line contamination. We confirm previously known conclusions on firmer quantitative grounds in particular by improving the measurements at z ∼ 1. Two flux statistics at 0 & F & 1, the mean H i flux and the flux probability distribution function (PDF), show that considerable evolution occurs from z = 3.6 to z = 1.5, after which it slows down to become effectively stable for z & 0.5. However, there are large sightline variations. For the H i column density distribution function (CDDF, f ∝ $N_{\\rm H\\,{\\small I}}^{-\\beta }$) at $\\log (N_{\\mathrm{H\\,{\\small I}}}/1\\, {\\mathrm{cm}^{-2}})$ ∈ [13.5, 16.0], β increases as z decreases from β = 1.60 at z ∼ 3.4 to β = 1.82 at z ∼ 0.1. The CDDF shape at lower redshifts can be reproduced by a small amount of clockwise rotation of a higher-z CDDF with a slightly larger CDDF normalization. The absorption line number per z (dn/dz) shows a similar evolutionary break at z ∼ 1.5 as seen in the flux statistics. High-$N_{\\mathrm{H\\,{\\small I}}}$ absorbers evolve more rapidly than low-$N_{\\mathrm{H\\,{\\small I}}}$ absorbers to decrease in number or cross-section with time. The in idual dn/dz shows a large scatter at a given z. The scatter increases towards lower z, possibly caused by a stronger clustering at lower z.
Publisher: Oxford University Press (OUP)
Date: 15-05-2014
DOI: 10.1093/MNRAS/STU660
Publisher: Oxford University Press (OUP)
Date: 25-08-2016
Publisher: Oxford University Press (OUP)
Date: 07-11-2017
Publisher: Oxford University Press (OUP)
Date: 09-01-2014
Publisher: Oxford University Press (OUP)
Date: 10-12-2007
Publisher: Oxford University Press (OUP)
Date: 10-12-2015
Publisher: Oxford University Press (OUP)
Date: 21-11-2007
Publisher: American Physical Society (APS)
Date: 18-11-2022
Publisher: Oxford University Press (OUP)
Date: 11-03-2006
Publisher: Oxford University Press (OUP)
Date: 19-12-2022
Abstract: Enhanced ionizing radiation in close proximity to redshift z ≳ 6 quasars creates short windows of intergalactic Ly α transmission blueward of the quasar Ly α emission lines. The majority of these Ly α near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\\rm Q}\\sim 10^{5}\\!-\\!10^{7}\\rm \\, yr$. However, lifetimes as short as $t_{\\rm Q}\\lesssim 10^{4}\\rm \\, yr$ appear to be required by the smallest Ly α near-zones. These short lifetimes present an apparent challenge for the growth of $\\sim 10^{9}\\rm \\, M_{\\odot }$ black holes at z ≳ 6. Accretion over longer time-scales is only possible if black holes grow primarily in an obscured phase, or if the quasars are variable on time-scales comparable to the equilibriation time for ionized hydrogen. Distinguishing between very young quasars and older quasars that have experienced episodic accretion with Ly α absorption alone is challenging, however. We therefore predict the signature of proximate 21-cm absorption around z ≳ 6 radio-loud quasars. For modest pre-heating of intergalactic hydrogen by the X-ray background, where the spin temperature $T_{\\rm S} \\lesssim 10^{2}\\rm \\, K$ prior to any quasar heating, we find proximate 21-cm absorption should be observable in the spectra of radio-loud quasars. The extent of the proximate 21-cm absorption is sensitive to the integrated lifetime of the quasar. Evidence for proximate 21-cm absorption from the diffuse intergalactic medium within $2\\!-\\!3\\rm \\, pMpc$ of a (radio-loud) quasar would be consistent with a short quasar lifetime, $t_{\\rm Q}\\lesssim 10^{5}\\rm \\, yr$, and would provide a complementary constraint on models for high-redshift black hole growth.
Publisher: Oxford University Press (OUP)
Date: 31-12-2013
Publisher: Oxford University Press (OUP)
Date: 21-09-2016
Publisher: Oxford University Press (OUP)
Date: 09-01-2015
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.45
Abstract: Determining when and how the first galaxies reionised the intergalactic medium promises to shed light on both the nature of the first objects and the cosmic history of baryons. Towards this goal, quasar absorption lines play a unique role by probing the properties of diffuse gas on galactic and intergalactic scales. In this review, we examine the multiple ways in which absorption lines trace the connection between galaxies and the intergalactic medium near the reionisation epoch. We first describe how the Ly α forest is used to determine the intensity of the ionising ultraviolet background and the global ionising emissivity budget. Critically, these measurements reflect the escaping ionising radiation from all galaxies, including those too faint to detect directly. We then discuss insights from metal absorption lines into reionisation-era galaxies and their surroundings. Current observations suggest a buildup of metals in the circumgalactic environments of galaxies over z ~ 6 to 5, although changes in ionisation will also affect the evolution of metal line properties. A substantial fraction of metal absorbers at these redshifts may trace relatively low-mass galaxies. Finally, we review constraints from the Ly α forest and quasar near zones on the timing of reionisation. Along with other probes of the high-redshift Universe, absorption line data are consistent with a relatively late end to reionisation (5.5 ≲ z ≲ 7) however, the constraints are still fairly week. Significant progress is expected to come through improved analysis techniques, increases in the number of known high-redshift quasars from optical and infrared sky surveys, large gains in sensitivity from next-generation observing facilities, and synergies with other probes of the reionisation era.
Publisher: American Astronomical Society
Date: 14-02-2019
Publisher: Oxford University Press (OUP)
Date: 09-03-2012
Publisher: Oxford University Press (OUP)
Date: 05-2008
Publisher: Oxford University Press (OUP)
Date: 18-10-2014
Publisher: Oxford University Press (OUP)
Date: 15-06-2016
Publisher: American Physical Society (APS)
Date: 29-01-2008
Publisher: Oxford University Press (OUP)
Date: 04-2019
Publisher: Oxford University Press (OUP)
Date: 09-2009
Publisher: Oxford University Press (OUP)
Date: 12-11-2016
Publisher: IOP Publishing
Date: 02-07-2014
Publisher: American Physical Society (APS)
Date: 05-08-2013
Publisher: Oxford University Press (OUP)
Date: 03-07-2012
Publisher: Oxford University Press (OUP)
Date: 21-09-2021
Abstract: The mean free path of ionizing photons, λmfp, is a key factor in the photoionization of the intergalactic medium (IGM). At z ≳ 5, however, λmfp may be short enough that measurements towards QSOs are biased by the QSO proximity effect. We present new direct measurements of λmfp that address this bias and extend up to z ∼ 6 for the first time. Our measurements at z ∼ 5 are based on data from the Giant Gemini GMOS survey and new Keck LRIS observations of low-luminosity QSOs. At z ∼ 6 we use QSO spectra from Keck ESI and VLT X-Shooter. We measure $\\lambda _{\\rm mfp} = 9.09^{+1.62}_{-1.28}$ proper Mpc and $0.75^{+0.65}_{-0.45}$ proper Mpc (68 per cent confidence) at z = 5.1 and 6.0, respectively. The results at z = 5.1 are consistent with existing measurements, suggesting that bias from the proximity effect is minor at this redshift. At z = 6.0, however, we find that neglecting the proximity effect biases the result high by a factor of two or more. Our measurement at z = 6.0 falls well below extrapolations from lower redshifts, indicating rapid evolution in λmfp over 5 & z & 6. This evolution disfavours models in which reionization ended early enough that the IGM had time to fully relax hydrodynamically by z = 6, but is qualitatively consistent with models wherein reionization completed at z = 6 or even significantly later. Our mean free path results are most consistent with late reionization models wherein the IGM is still 20 per cent neutral at z = 6, although our measurement at z = 6.0 is even lower than these models prefer.
Publisher: Oxford University Press (OUP)
Date: 31-12-2016
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
DOI: 10.1093/MNRAS/STS455
Publisher: Oxford University Press (OUP)
Date: 26-04-2012
Publisher: Oxford University Press (OUP)
Date: 24-11-2011
Publisher: Oxford University Press (OUP)
Date: 11-05-2009
Publisher: Oxford University Press (OUP)
Date: 21-07-2011
Publisher: Oxford University Press (OUP)
Date: 2007
Publisher: Oxford University Press (OUP)
Date: 23-09-1211
Publisher: Oxford University Press (OUP)
Date: 21-07-2021
Abstract: Local variations in the intergalactic medium (IGM) neutral hydrogen fraction will affect the Ly α absorption signature of protoclusters identified in tomographic surveys. Using the IllustrisTNG simulations, we investigate how the AGN proximity effect and hot, collisionally ionized gas arising from gravitational infall and black hole feedback changes the Ly α absorption associated with $M_{z=0}\\simeq 10^{14}\\, {\\rm M}_\\odot$ protoclusters at z ≃ 2.4. We find that protocluster galaxy overdensities exhibit a weak anticorrelation with Ly α transmission in IGM transmission maps, but local H$\\, \\rm \\scriptstyle I$ ionization enhancements due to hot $T\\gt 10^{6}\\rm \\, K$ gas or nearby AGN can disrupt this relationship within in idual protoclusters. On average, however, we find that strong reductions in the IGM neutral fraction are limited to within $\\lesssim 5h^{-1}\\, \\textrm {cMpc}$ of the dark matter haloes. Local ionization enhancements will therefore have a minimal impact on the completeness of protocluster identification in tomographic surveys if smoothing Ly α transmission maps over scales of $\\sim 4 h^{-1}\\, \\textrm {cMpc}$, as is typically done in observations. However, if calibrating the relationship between the matter density and Ly α transmission in tomographic maps using simple analytical models for the Ly α forest opacity, the presence of hot gas around haloes can still result in systematically lower estimates of Mz = 0 for the most massive protoclusters.
Publisher: Oxford University Press (OUP)
Date: 23-01-2017
DOI: 10.1093/MNRAS/STX191
Publisher: Oxford University Press (OUP)
Date: 02-07-2015
Publisher: EDP Sciences
Date: 07-2014
Publisher: EDP Sciences
Date: 11-2013
Publisher: Oxford University Press (OUP)
Date: 14-10-2014
Publisher: American Physical Society (APS)
Date: 19-07-2017
Publisher: Oxford University Press (OUP)
Date: 11-10-2009
Publisher: Oxford University Press (OUP)
Date: 12-08-2015
Publisher: Oxford University Press (OUP)
Date: 16-10-2013
Publisher: Oxford University Press (OUP)
Date: 22-08-2015
Publisher: Oxford University Press (OUP)
Date: 26-11-2021
Abstract: We use the Sherwood–Relics suite of hybrid hydrodynamical and radiative transfer simulations to model the effect of inhomogeneous reionization on the 1D power spectrum of the Lyman α (Lyα) forest transmitted flux at redshifts 4.2 ≤ z ≤ 5. Relative to models that assume a homogeneous ultraviolet background, reionization suppresses the power spectrum at small scales, k ∼ 0.1 km−1 s, by ∼10 per cent because of spatial variations in the thermal broadening kernel and the ergent peculiar velocity field associated with overpressurized intergalactic gas. On larger scales, $k\\lt 0.03\\rm \\, km^{-1}\\, s$, the power spectrum is instead enhanced by 10–50 per cent by large-scale spatial variations in the neutral hydrogen fraction. The effect of inhomogeneous reionization must therefore be accounted for in analyses of forthcoming high precision measurements. We provide a correction for the Lyα forest power spectrum at 4.1 ≤ z ≤ 5.4 that can be easily applied within other parameter inference frameworks using similar reionization models. We perform a Bayesian analysis of mock data to assess the extent of systematic biases that may arise in measurements of the intergalactic medium if ignoring this correction. At the scales probed by current high-resolution Lyα forest data at z & 4, $0.006 \\le k \\le 0.2 \\rm \\, km^{-1}\\, s$, we find inhomogeneous reionization does not introduce any significant bias in thermal parameter recovery for the current measurement uncertainties of ∼10 per cent. However, for 5 per cent uncertainties, ∼1σ shifts between the estimated and true parameters occur.
Publisher: Oxford University Press (OUP)
Date: 23-04-2012
Publisher: American Physical Society (APS)
Date: 20-07-2017
Publisher: Oxford University Press (OUP)
Date: 10-2007
Publisher: Oxford University Press (OUP)
Date: 09-04-2020
Abstract: We compare a s le of five high-resolution, high S/N Ly α forest spectra of bright 6 & z & ∼6.5 QSOs aimed at spectrally resolving the last remaining transmission spikes at z & 5 with those obtained from mock absorption spectra from the Sherwoodand Sherwood–Relics simulation suites of hydrodynamical simulations of the intergalactic medium (IGM). We use a profile-fitting procedure for the inverted transmitted flux, 1 − F, similar to the widely used Voigt profile fitting of the transmitted flux F at lower redshifts, to characterize the transmission spikes that probe predominately underdense regions of the IGM. We are able to reproduce the width and height distributions of the transmission spikes, both with optically thin simulations of the post-reionization Universe using a homogeneous UV background and full radiative transfer simulations of a late reionization model. We find that the width of the fitted components of the simulated transmission spikes is very sensitive to the instantaneous temperature of the reionized IGM. The internal structures of the spikes are more prominent in low temperature models of the IGM. The width distribution of the observed transmission spikes, which require high spectral resolution (≤ 8 km s−1) to be resolved, is reproduced for optically thin simulations with a temperature at mean density of T0 = (11 000 ± 1600, 10 500 ± 2100, 12 000 ± 2200) K at z = (5.4, 5.6, 5.8). This is weakly dependent on the slope of the temperature-density relation, which is favoured to be moderately steeper than isothermal. In the inhomogeneous, late reionization, full radiative transfer simulations where islands of neutral hydrogen persist to z ∼ 5.3, the width distribution of the observed transmission spikes is consistent with the range of T0 caused by spatial fluctuations in the temperature–density relation.
Publisher: Oxford University Press (OUP)
Date: 20-05-2015
DOI: 10.1093/MNRAS/STV773
Publisher: Oxford University Press (OUP)
Date: 07-2021
Abstract: A late end to reionisation at redshift z ≃ 5.3 is consistent with observed spatial variations in the Lyα forest transmission and the deficit of Lyα emitting galaxies around extended Lyα absorption troughs at z = 5.5. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until z ≃ 6. We use a novel, hybrid approach that combines high resolution cosmological hydrodynamical simulations with radiative transfer to predict the incidence of strong $21\\rm \\, cm$ forest absorbers with optical depths τ21 & 10−2 from the diffuse IGM in these late reionisation models. We include the effect of redshift space distortions on the simulated $21\\rm \\, cm$ forest spectra, and treat the highly uncertain heating of the pre-reionisation IGM by soft X-rays as a free parameter. For a model with only modest IGM pre-heating, such that average gas kinetic temperatures in the diffuse IGM remain below $T_{\\rm K}\\simeq 10^{2} \\rm \\, K$, we find that strong $21\\rm \\, cm$ forest absorption lines should persist until z = 6. For a s le of ∼10 sufficiently radio loud background sources, a null-detection of $21\\rm \\, cm$ forest absorbers at z ≃ 6 with SKA1-low or possibly LOFAR should provide an informative lower limit on the still largely unconstrained soft X-ray background at high redshift and the temperature of the pre-reionisation IGM.
Publisher: Oxford University Press (OUP)
Date: 11-07-2009
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for James Bolton.