High Resolution Observations of Neutral Hydrogen in M33 -- I: The Hydrogen Distribution

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.

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Search for HI Bubbles Around WR Stars: WR 149

Symposium - International Astronomical Union ◽

10.1017/s0074180900230465 ◽

1996 ◽

Vol 169 ◽

pp. 619-620

Author(s):

C. Cappa de Nicolau ◽

V.S. Niemela ◽

U. Herbstmeier ◽

B. Koribalski

Keyword(s):

Interstellar Medium ◽

Neutral Hydrogen ◽

Gas Bubbles ◽

Stellar Winds ◽

Hydrogen Distribution ◽

Neutral Gas ◽

Rayet Star

The interaction of strong stellar winds with the interstellar medium creates large cavities or interstellar bubbles surrounded by expanding outer shells. 21-cm line (HI) observations have revealed the presence of such neutral gas bubbles around several WR stars (e.g. Niemela & Cappa de Nicolau 1991 and references therein; Dubner et al. 1992).Continuing our search for HI bubbles around WR stars, we have analyzed the neutral hydrogen distribution in the vicinity of the Wolf-Rayet star WR149, a highly reddened WN6-7 star located at 6.5 kpc in the direction (l,b) = (89.°53,+0.°65).

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900240771 ◽

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.

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High-redshift test of gravity using enhanced growth of small structures probed by the neutral hydrogen distribution

Physical Review D ◽

10.1103/physrevd.100.064044 ◽

2019 ◽

Vol 100 (6) ◽

Author(s):

Matteo Leo ◽

Christian Arnold ◽

Baojiu Li

Keyword(s):

High Redshift ◽

Neutral Hydrogen ◽

Hydrogen Distribution

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The Gaseous Content of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900005234 ◽

1972 ◽

Vol 44 ◽

pp. 12-36 ◽

Cited By ~ 4

Author(s):

Morton S. Roberts

Keyword(s):

Neutral Hydrogen ◽

Hubble Constant ◽

Type Systems ◽

Systematic Difference ◽

Optical Center ◽

Hydrogen Distribution ◽

Interstellar Gas ◽

A Value ◽

Galaxy Type ◽

The Difference

A general review is given of the content and distribution of interstellar gas within galaxies. The constancy of the ratio N(He)/N(H), independent of galaxy type (spirals and irregulars), is discussed and the possible mechanisms for this constancy are considered. The helium abundance does not vary across the disk of spirals, although nitrogen and possibly other elements do.The gross features of the neutral hydrogen distribution in our Galaxy and other systems are described. In spirals, the peak of the radial distribution of Hi is located well away from the optical center. This is not the case for irregular-type systems. A possible correlation of the relative location of the maxima of Hi and Hii distributions with galaxy type is described. Many spirals studied with high enough relative angular resolution show concentrations of Hi in their outermost regions. These may be due to hydrogen companions or warps in the hydrogen plane. Hydrogen ‘bridges’ are described and a new example for the triple system M81–M82–NGC 3077 is given. This latter case may be an extreme example of distortion by companion galaxies of the Hi associated with a massive galaxy.The neutral hydrogen content of a galaxy and its correlation with other integral properties is discussed. The absorption profile due to hydrogen associated with the radio galaxy Centaurus A is given. Comparison of optical and 21-cm measurements of galaxian redshifts shows excellent agreement over the radical velocity range −400 to + 5200 km s−1. There is, however, a systematic difference between 21 cm and optical redshifts over the range ∼ 1200 to ∼ 2400 km s−1 for optical values based on blue-sensitive spectra. The difference, ∼ 100 km s−1, is most likely due to blending of galaxian and night sky H and K absorption lines. The Hubble Constant is derived from a redshift-21 cm flux relation. Values in the range 78 to 109 km s−1 Mpc−1 are derived. A value of 97 kms−1 Mpc−1 is favored.

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

The Astrophysical Journal ◽

10.1086/153301 ◽

1975 ◽

Vol 195 ◽

pp. 23 ◽

Cited By ~ 30

Author(s):

S. T. Gottesman ◽

L. Weliachew

Keyword(s):

High Resolution ◽

Neutral Hydrogen ◽

The Galaxy

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937112 ◽

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.

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