scholarly journals Long troughs in the Lyman-α forest below redshift 6 due to islands of neutral hydrogen

2019 ◽  
Vol 491 (2) ◽  
pp. 1736-1745 ◽  
Author(s):  
Laura C Keating ◽  
Lewis H Weinberger ◽  
Girish Kulkarni ◽  
Martin G Haehnelt ◽  
Jonathan Chardin ◽  
...  
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
Neutral Hydrogen

ABSTRACT A long (110 cMpc h−1) and deep absorption trough in the Ly α forest has been observed extending down to redshift 5.5 in the spectrum of ULAS J0148+0600. Although no Ly α transmission is detected, Ly β spikes are present which has led to claims that the gas along this trough must be ionized. Using high-resolution cosmological radiative transfer simulations in large volumes, we show that in a scenario where reionization ends late (z ∼ 5.2), our simulations can reproduce troughs as long as observed. In this model, we find that the troughs are caused by islands of neutral hydrogen. Small ionized holes within the neutral islands allow for the transmission of Ly β. We have also modelled the Ly α emitter population around the simulated troughs, and show that there is a deficit of Ly α emitters close to the trough as is observed.

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 High Resolution Observations of Neutral Hydrogen in M33 - II: THE VELOCITY FIELD

1973 ◽  
Vol 163 (2) ◽  
pp. 163-182 ◽  
Author(s):  
P. J. Warner ◽  
M. C. H. Wright ◽  
J. E. Baldwin
Keyword(s):  
High Resolution ◽  
Velocity Field ◽  
Neutral Hydrogen

scholarly journals High-resolution near-infrared speckle interferometry and radiative transfer modeling of the OH/IR star OH 104.9+2.4

2004 ◽  
Vol 424 (1) ◽  
pp. 165-177 ◽  
Author(s):  
D. Riechers ◽  
Y. Balega ◽  
T. Driebe ◽  
K.-H. Hofmann ◽  
A. B. Men'shchikov ◽  
...  
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
Near Infrared ◽  
Speckle Interferometry ◽  
Radiative Transfer Modeling

scholarly journals The Relationship Between Gas and Cirrus Dust Filaments at the Edge of the Expanding Shell in Eridanus

1990 ◽  
Vol 139 ◽  
pp. 235-236
Author(s):  
G. L. Verschuur ◽  
F. Verter ◽  
L. J. Rickard ◽  
D. T. Leisawitz
Keyword(s):  
High Resolution ◽  
Surface Brightness ◽  
Neutral Hydrogen ◽  
Scale Structure ◽  
Small Scale ◽  
Molecular Gas ◽  
Small Scale Structure ◽  
Point To Point ◽  
The Relationship ◽  
Co Observations

At the boundary of a large expanding shell in Eridanus around l = 187°, b = −50° the morphology observed in the HI emission is well mimicked by the 100 μm surface brightness but with associated structures offset by as much as 0.°5. A point-to-point comparison between I100μm and NHI in filaments of neutral hydrogen and dust (IR cirrus) produces only a weak dependence. However, when I100μm at a cirrus dust peak is compared with NHI at the associated H i peak, a relationship closer to that reported by other workers is found. Preliminary CO observations have set low limits on the molecular gas in these filaments. Since the H i and dust in our region are associated with a large expanding shell (or superbubble), shocks may be responsible for separation of gas and dust. The existence of small-scale structure in both the HI and IR is noted. We conclude that attempts to correlate HI and IR must invoke high-resolution area surveys.

scholarly journals High resolution and Monte Carlo additions to the SASKTRAN radiative transfer model

2015 ◽  
Vol 8 (3) ◽  
pp. 3357-3397 ◽  
Author(s):  
D. J. Zawada ◽  
S. R. Dueck ◽  
L. A. Rieger ◽  
A. E. Bourassa ◽  
N. D. Lloyd ◽  
...  
Keyword(s):  
Monte Carlo ◽  
High Resolution ◽  
Radiative Transfer ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Reference Model ◽  
Monte Carlo Model ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Systematic Bias

Abstract. The OSIRIS instrument on board the Odin spacecraft has been measuring limb scattered radiance since 2001. The vertical radiance profiles measured as the instrument nods are inverted, with the aid of the SASKTRAN radiative transfer model, to obtain vertical profiles of trace atmospheric constituents. Here we describe two newly developed modes of the SASKTRAN radiative transfer model: a high spatial resolution mode, and a Monte Carlo mode. The high spatial resolution mode is a successive orders model capable of modelling the multiply scattered radiance when the atmosphere is not spherically symmetric; the Monte Carlo mode is intended for use as a highly accurate reference model. It is shown that the two models agree in a wide variety of solar conditions to within 0.2%. As an example case for both models, Odin-OSIRIS scans were simulated with the Monte Carlo model and retrieved using the high resolution model. A systematic bias of up to 4% in retrieved ozone number density between scans where the instrument is scanning up or scanning down was identified. It was found that calculating the multiply scattered diffuse field at five discrete solar zenith angles is sufficient to eliminate the bias for typical Odin-OSIRIS geometries.

A high-resolution neutral-hydrogen study of the galaxy M81

1975 ◽  
Vol 195 ◽  
pp. 23 ◽  
Author(s):  
S. T. Gottesman ◽  
L. Weliachew
Keyword(s):  
High Resolution ◽  
Neutral Hydrogen ◽  
The Galaxy

scholarly journals High spin temperatures at large impact parameters: Ionisation in the outskirts of galaxies

2020 ◽  
Vol 635 ◽  
pp. A166
Author(s):  
S. J. Curran
Keyword(s):  
Temperature Distribution ◽  
High Resolution ◽  
Impact Parameter ◽  
Column Density ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Neutral Hydrogen ◽  
Spin Temperature ◽  
The Mean ◽  
Impact Parameters

By including the most recent observations of H I 21-cm absorption through nearby galactic discs, we confirm our previous assertion that there is an anti-correlation between the abundance of cool neutral atomic gas and impact parameter. In comparing the measured neutral hydrogen column densities of the sample with the absorption strength, we find a peak in the mean spin temperature of ⟨Tspin/f ⟩ ≈ 2310 K at an impact parameter of ρ ≈ 14 kpc, with ⟨Tspin/f ⟩≳1000 K in the remainder of the disc. This is significantly different to the spin temperature distribution in the Milky Way, which exhibits a constant ≈250 − 400 K over ρ = 8 − 25 kpc. The measured column densities may, however, suffer from beam dilution, which we show appears to be the case for the observations of H I 21-cm emission in which the beam subtends radii of ≳10 kpc. We therefore applied the column density profile of the Milky Way, in addition to the mean of the sample, observed at sufficiently high resolution, and the mean profile for the nearby ∼1012 M⊙ galaxies in the IllustrisTNG simulations. All of the models yield a peak in the mean spin temperature at similar impact parameters (r ≈ 10 − 15 kpc) as the measured column densities. These radii are similar to those of the spiral arms where H II regions are often concentrated. We therefore suggest that the elevated spin temperatures trace the H II regions observed in the outer disc of many spiral galaxies.

scholarly journals Hot bubbles of planetary nebulae with hydrogen-deficient winds

2018 ◽  
Vol 620 ◽  
pp. A98 ◽  
Author(s):  
R. Heller ◽  
R. Jacob ◽  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Thermal Conduction ◽  
Thermal Structure ◽  
Neutral Hydrogen ◽  
Planetary Nebulae ◽  
Chemical Compositions ◽  
Heat Conducting ◽  
X Ray ◽  
Similar Solutions

Context. The first high-resolution X-ray spectroscopy of a planetary nebula, BD +30° 3639, opened the possibility to study plasma conditions and chemical compositions of X-ray emitting “hot” bubbles of planetary nebulae in much greater detail than before. Aims. We investigate (i) how diagnostic line ratios are influenced by the bubble’s thermal structure and chemical profile, (ii) whether the chemical composition inside the bubble of BD +30° 3639 is consistent with the hydrogen-poor composition of the stellar photosphere and wind, and (iii) whether hydrogen-rich nebular matter has already been added to the bubble of BD +30° 3639 by evaporation. Methods. We applied an analytical, one-dimensional (1D) model for wind-blown bubbles with temperature and density profiles based on self-similar solutions including thermal conduction. We also constructed heat-conduction bubbles with a chemical stratification. The X-ray emission was computed using the well-documented CHIANTI code. These bubble models are used to re-analyse the high-resolution X-ray spectrum from the hot bubble of BD +30° 3639. Results. We found that our 1D heat-conducting bubble models reproduce the observed line ratios much better than plasmas with single electron temperatures. In particular, all the temperature- and abundance-sensitive line ratios are consistent with BD +30° 3639 X-ray observations for (i) an intervening column density of neutral hydrogen, NH = 0.20-0.10+0.05 × 1022cm−2, (ii) a characteristic bubble X-ray temperature of TX = 1.8 ± 0.1 MK together with (iii) a very high neon mass fraction of about 0.05, virtually as high as that of oxygen. For lower values of NH, we cannot exclude the possibility that the hot bubble of BD +30° 3639 contains a small amount of “evaporated” (or mixed) hydrogen-rich nebular matter. Given the possible range of NH, the fraction of evaporated hydrogen-rich matter cannot exceed 3% of the bubble mass. Conclusions. The diffuse X-ray emission from BD +30° 3639 can be well explained by models of wind-blown bubbles with thermal conduction and a chemical composition equal to that of the hydrogen-poor and carbon-, oxygen-, and neon-rich stellar surface.

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