Extragalactic diffuse neutral hydrogen clouds - Probes of a hot intergalactic medium

1976 ◽  
Vol 209 ◽  
pp. L105 ◽  
Author(s):  
L. L. Cowie ◽  
C. F. McKee
Keyword(s):  
Intergalactic Medium ◽  
Neutral Hydrogen

scholarly journals Probing the thermal state of the intergalactic medium at z > 5 with the transmission spikes in high-resolution  Ly α forest spectra

2020 ◽  
Vol 494 (4) ◽  
pp. 5091-5109 ◽  
Author(s):  
Prakash Gaikwad ◽  
Michael Rauch ◽  
Martin G Haehnelt ◽  
Ewald Puchwein ◽  
James S Bolton ◽  
...  
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
Intergalactic Medium ◽  
Thermal State ◽  
Neutral Hydrogen ◽  
High Spectral Resolution ◽  
Profile Fitting ◽  
Density Relation ◽  
Width Distribution ◽  
Hydrodynamical Simulations

ABSTRACT We compare a sample 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.

scholarly journals The H i bias during the Epoch of Reionization

2019 ◽  
Vol 490 (4) ◽  
pp. 5739-5748 ◽  
Author(s):  
Wenxiao Xu ◽  
Yidong Xu ◽  
Bin Yue ◽  
Ilian T Iliev ◽  
Hy Trac ◽  
...  
Keyword(s):  
Late Stage ◽  
Intergalactic Medium ◽  
Early Stage ◽  
Neutral Hydrogen ◽  
Scale Dependence ◽  
Neutral Fraction ◽  
Matter Distribution ◽  
Absolute Value ◽  
Small Scales

ABSTRACT The neutral hydrogen (H i) and its 21 cm line are promising probes to the reionization process of the intergalactic medium (IGM). To use this probe effectively, it is imperative to have a good understanding on how the neutral hydrogen traces the underlying matter distribution. Here, we study this problem using seminumerical modelling by combining the H i in the IGM and the H i from haloes during the epoch of reionization (EoR), and investigate the evolution and the scale dependence of the neutral fraction bias as well as the 21 cm line bias. We find that the neutral fraction bias on large scales is negative during reionization, and its absolute value on large scales increases during the early stage of reionization and then decreases during the late stage. During the late stage of reionization, there is a transition scale at which the H i bias transits from negative on large scales to positive on small scales, and this scale increases as the reionization proceeds to the end.

scholarly journals Using realistic host galaxy metallicities to improve the GRB X-ray equivalent total hydrogen column density and constrain the intergalactic medium density

2020 ◽  
Vol 495 (2) ◽  
pp. 2342-2353
Author(s):  
Tony Dalton ◽  
Simon L Morris
Keyword(s):  
Column Density ◽  
Intergalactic Medium ◽  
Neutral Hydrogen ◽  
Accurate Estimate ◽  
Host Galaxy ◽  
Lower Envelope ◽  
Sample Mean ◽  
X Ray ◽  
Hydrogen Column Density ◽  
Solar Metallicity

ABSTRACT It is known that the GRB equivalent hydrogen column density (NHX) changes with redshift and that, typically, NHX is greater than the GRB host neutral hydrogen column density. We have compiled a large sample of data for GRB NHX and metallicity [X/H]. The main aims of this paper are to generate improved NHX for our sample by using actual metallicities, dust corrected where available for detections, and for the remaining GRB, a more realistic average intrinsic metallicity using a standard adjustment from solar. Then, by approximating the GRB host intrinsic hydrogen column density using the measured neutral column (NHI, IC) adjusted for the ionization fraction, we isolate a more accurate estimate for the intergalactic medium (IGM) contribution. The GRB sample mean metallicity is = −1.17 ± 0.09 rms (or 0.07 ± 0.05 Z/Zsol) from a sample of 36 GRB with a redshift 1.76 ≤ z ≤ 5.91, substantially lower than the assumption of solar metallicity used as standard for many fitted NHX. Lower GRB host mean metallicity results in increased estimated NHX with the correction scaling with redshift as Δlog (NHX cm−2) = (0.59 ± 0.04)log(1 + z) + 0.18 ± 0.02. Of the 128 GRB with data for both NHX and NHI, IC in our sample, only six have NHI, IC > NHX when revised for realistic metallicity, compared to 32 when solar metallicity is assumed. The lower envelope of the revised NHX – NHI, IC, plotted against redshift can be fit by log(NHX – NHI, IC cm−2) = 20.3 + 2.4 log(1 + z). This is taken to be an estimate for the maximum IGM hydrogen column density as a function of redshift. Using this approach, we estimate an upper limit to the hydrogen density at redshift zero (n0) to be consistent with n0 = 0.17 × 10−7cm−3.

scholarly journals SILVERRUSH. XI. Constraints on the Lyα Luminosity Function and Cosmic Reionization at z = 7.3 with Subaru/Hyper Suprime-Cam

2021 ◽  
Vol 923 (2) ◽  
pp. 229
Author(s):  
Hinako Goto ◽  
Kazuhiro Shimasaku ◽  
Satoshi Yamanaka ◽  
Rieko Momose ◽  
Makoto Ando ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Intergalactic Medium ◽  
Neutral Hydrogen ◽  
Neutral Fraction ◽  
Estimation Methods ◽  
Large Area ◽  
Upper Limit ◽  
Narrowband Imaging ◽  
First Time

Abstract The Lyα luminosity function (LF) of Lyα emitters (LAEs) has been used to constrain the neutral hydrogen fraction in the intergalactic medium (IGM) and thus the timeline of cosmic reionization. Here we present the results of a new narrowband imaging survey for z = 7.3 LAEs in a large area of ∼3 deg2 with Subaru/Hyper Suprime-Cam. No LAEs are detected down to L Lyα ≃ 1043.2 erg s−1 in an effective cosmic volume of ∼2 × 106 Mpc3, placing an upper limit on the bright part of the z = 7.3 Lyα LF for the first time and confirming a decrease in bright LAEs from z = 7.0. By comparing this upper limit with the Lyα LF in the case of fully ionized IGM, which is predicted using an observed z = 5.7 Lyα LF on the assumption that the intrinsic Lyα LF evolves in the same way as the UV LF, we obtain the relative IGM transmission T Ly α IGM ( 7.3 ) / T Ly α IGM ( 5.7 ) < 0.77 and then the volume-averaged neutral fraction x H I(7.3) > 0.28. Cosmic reionization is thus still ongoing at z = 7.3, consistent with results from other x H I estimation methods. A similar analysis using literature Lyα LFs finds that at z = 6.6 and 7.0, the observed Lyα LF agrees with the predicted one, consistent with full ionization.

scholarly journals Implications of the z > 5 Lyman-α forest for the 21-cm power spectrum from the epoch of reionization

2021 ◽  
Author(s):  
Janakee Raste ◽  
Girish Kulkarni ◽  
Laura C Keating ◽  
Martin G Haehnelt ◽  
Jonathan Chardin ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Power Spectrum ◽  
Intergalactic Medium ◽  
Neutral Hydrogen ◽  
Redshift Range ◽  
Sky Temperature ◽  
Conventional Models

Abstract Our understanding of the intergalactic medium at redshifts z = 5–6 has improved considerably in the last few years due to the discovery of quasars with z &gt; 6 that enable Lyman-α forest studies at these redshifts. A realisation from this has been that hydrogen reionization could end much later than previously thought, so that large “islands” of cold, neutral hydrogen could exist in the IGM at redshifts z = 5–6. By using radiative transfer simulations of the IGM, we consider the implications of the presence of these neutral hydrogen islands for the 21-cm power spectrum signal and its potential detection by experiments such as hera, ska, lofar, and mwa. In contrast with previous models of the 21-cm signal, we find that thanks to the late end of reionization the 21-cm power in our simulation continues to be as high as $\Delta ^2_{21}=10~\mathrm{mK}^2$ at k ∼ 0.1 h cMpc−1 at z = 5–6. This value of the power spectrum is several orders of magnitude higher than that in conventional models considered in the literature for these redshifts. Such high values of the 21-cm power spectrum should be detectable by hera and ska1-low in ∼1000 hours, assuming optimistic foreground subtraction. This redshift range is also attractive due to relatively low sky temperature and potentially greater abundance of multiwavelength data.

Neutral Hydrogen Gunn‐Peterson Absorption from an Overdensity in the Diffuse Intergalactic Medium at Redshift 0.8?

1997 ◽  
Vol 491 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Valery K. Khersonsky ◽  
David A. Turnshek ◽  
Sheflynn M. Strub
Keyword(s):  
Intergalactic Medium ◽  
Neutral Hydrogen

scholarly journals GALEX colours of quasars and intergalactic medium opacity at low redshift

2019 ◽  
Vol 623 ◽  
pp. A149 ◽  
Author(s):  
J.-M. Deharveng ◽  
B. Milliard ◽  
C. Péroux ◽  
T. Small
Keyword(s):  
Power Law ◽  
Column Density ◽  
Intergalactic Medium ◽  
Uv Spectroscopy ◽  
Broad Band ◽  
Neutral Hydrogen ◽  
Redshift Distribution ◽  
Density Distributions ◽  
A Value ◽  
Power Law Index

Aims. The distribution of neutral hydrogen in the intergalactic medium (IGM) is currently explored at low redshift by means of UV spectroscopy of quasars. We propose here an alternative approach based on UV colours of quasars as observed from GALEX surveys. We built a NUV-selected sample of 9033 quasars with (FUV−NUV) colours. The imprint of HI absorption in the observed colours is suggested qualitatively by their distribution as a function of quasar redshift. Methods. Because broad band fluxes lack spectral resolution and are sensitive to a large range of HI column densities a Monte Carlo simulation of IGM opacity is required for quantitative analysis. It was performed with absorbers randomly distributed along redshift and column density distributions. The column density distribution was assumed to be a broken power law with index β1 (1015 cm−2 <  NHI <  1017.2 cm−2) and β2 (1017.2 cm−2 <  NHI <  1019 cm−2). For convenience the redshift distribution is taken proportional to the redshift evolution law of the number density of Lyman limit systems (LLS) per unit redshift as determined by existing spectroscopic surveys. The simulation is run with different assumptions on the spectral index αν of the quasar ionising flux. Results. The fits between the simulated and observed distribution of colours require an LLS redshift density larger than that derived from spectroscopic counting. This result is robust in spite of difficulties in determining the colour dispersion other than that due to neutral hydrogen absorption. This difference decreases with decreasing αν (softer ionising quasar spectrum) and would vanish only with values of αν which are not supported by existing observations. Conclusions. We provide arguments to retain αν = −2, a value already extreme with respect to those measured with HST/COS. Further fitting of power law index β1 and β2 leads to a higher density by a factor of 1.7 (β1 = −1.7, β2 = −1.5), possibly 1.5 (β1 = −1.7, β2 = −1.7). Beyond the result in terms of density the analysis of UV colours of quasars reveals a tension between the current description of IGM opacity at low z and the published average ionising spectrum of quasars.

scholarly journals Constraints on the End of Reionization from the Density Fields Surrounding Two Highly Opaque Quasar Sightlines

2021 ◽  
Vol 923 (1) ◽  
pp. 87
Author(s):  
Holly M. Christenson ◽  
George D. Becker ◽  
Steven R. Furlanetto ◽  
Frederick B. Davies ◽  
Matthew A. Malkan ◽  
...  
Keyword(s):  
Large Scale ◽  
Intergalactic Medium ◽  
Neutral Hydrogen ◽  
Large Fluctuations ◽  
First Time ◽  
The Relationship

Abstract The observed large-scale scatter in Lyα opacity of the intergalactic medium at z < 6 implies large fluctuations in the neutral hydrogen fraction that are unexpected long after reionization has ended. A number of models have emerged to explain these fluctuations that make testable predictions for the relationship between Lyα opacity and density. We present selections of z = 5.7 Lyα-emitting galaxies (LAEs) in the fields surrounding two highly opaque quasar sightlines with long Lyα troughs. The fields lie toward the z = 6.0 quasar ULAS J0148+0600, for which we reanalyze previously published results using improved photometric selection, and toward the z = 6.15 quasar SDSS J1250+3130, for which results are presented here for the first time. In both fields, we report a deficit of LAEs within 20 h −1 Mpc of the quasar. The association of highly opaque sightlines with galaxy underdensities in these two fields is consistent with models in which the scatter in Lyα opacity is driven by large-scale fluctuations in the ionizing UV background or by an ultra-late reionization that has not yet concluded at z = 5.7.

scholarly journals Evolution of neutral oxygen during the epoch of reionization and its use in estimating the neutral hydrogen fraction

2019 ◽  
Vol 489 (2) ◽  
pp. 2755-2768 ◽  
Author(s):  
Caitlin Doughty ◽  
Kristian Finlator
Keyword(s):  
Incidence Rate ◽  
Equivalent Width ◽  
Qualitative Agreement ◽  
Intergalactic Medium ◽  
Neutral Hydrogen ◽  
Line Of Sight ◽  
Ionization State ◽  
Total Oxygen ◽  
Ionization Fronts ◽  
Circumgalactic Medium

Abstract We use synthetic sightlines drawn through snapshots of the Technicolour Dawn simulations to explore how the statistics of neutral oxygen (${\mathrm{O}\,{\small I}}$) absorbers respond to hydrogen reionization. The ionization state of the circumgalactic medium (CGM) initially roughly tracks that of the intergalactic medium, but beginning at z = 8 the CGM grows systematically more neutral owing to self-shielding. Weak absorbers trace diffuse gas that lies farther from haloes, hence they are ionized first, whereas stronger systems are less sensitive to reionization. The overall ${\mathrm{O}\,{\small I}}$ covering fraction decreases slowly with time owing to competition between ongoing enrichment and gradual encroachment of ionization fronts into increasingly overdense gas. While the declining covering fraction is partially offset by continued formation of new haloes, the ionization of the diffuse gas causes the predicted line-of-sight incidence rate of ${\mathrm{O}\,{\small I}}$ absorbers to decline abruptly at the overlap epoch, in qualitative agreement with observations. In comparison to the recently observed equivalent width (EW) distribution at z ≈ 6, the simulations underproduce systems with $\mathrm{EW} \ge 0.1 \mathring{\rm A}$, although they reproduce weaker systems with $\mathrm{EW} \ge 0.05 \mathring{\rm A}$. By z ≈ 5, the incidence of $\mathrm{EW} \lt 0.1 \mathring{\rm A}$ systems are overproduced, consistent with previous indications that the simulated ionizing background is too weak at z &lt; 6. The summed column densities of $\mathrm{Si}\,{\small II}$ and $\mathrm{Si}\,{\small IV}$ trace the total oxygen column, and hence the ratio of the ${\mathrm{O}\,{\small I}}$ and $\mathrm{Si}\,{\small II}+ \mathrm{Si}\,{\small IV}$ comoving mass densities traces the progress of reionization. This probe may prove particularly useful in the regime where $x_{\mathrm{H}\,{\small I}} \gt 10{{\ \rm per\ cent}}$.

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