Motions of neutral hydrogen at high latitudes

1967 ◽  
Vol 31 ◽  
pp. 265-278 ◽  
Author(s):  
A. Blaauw ◽  
I. Fejes ◽  
C. R. Tolbert ◽  
A. N. M. Hulsbosch ◽  
E. Raimond
Keyword(s):  
Surface Density ◽  
Velocity Dispersion ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
High Latitudes ◽  
Low Velocity

Earlier investigations have shown that there is a preponderance of negative velocities in the hydrogen gas at high latitudes, and that in certain areas very little low-velocity gas occurs. In the region 100° <l< 250°, + 40° <b< + 85°, there appears to be a disturbance, with velocities between - 30 and - 80 km/sec. This ‘streaming’ involves about 3000 (r/100)2solar masses (rin pc). In the same region there is a low surface density at low velocities (|V| < 30 km/sec). About 40% of the gas in the disturbance is in the form of separate concentrations superimposed on a relatively smooth background. The number of these concentrations as a function of velocity remains constant from - 30 to - 60 km/sec but drops rapidly at higher negative velocities. The velocity dispersion in the concentrations varies little about 6·2 km/sec. Concentrations at positive velocities are much less abundant.

scholarly journals A Sky Survey of Neutral Hydrogen at l 21 cm. II. The Detailed Distribution of Low Velocity Gas

1963 ◽  
Vol 16 (1) ◽  
pp. 136 ◽  
Author(s):  
RX McGee ◽  
JD Murray ◽  
Janice A Milton
Keyword(s):  
Radial Velocity ◽  
Line Profile ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Hydrogen Line ◽  
Low Velocity ◽  
Sky Survey

The distributions of intensity and radial velocity of neutral hydrogen gas of low radial velocity are presented in the form of detailed diagrams of T max., the temperature at the peak of a hydrogen line profile, and of the radial velocity value at the Tmax .

scholarly journals Lyman α Emission from Disk Absorption Systems in QSOs: Star Formation in Young Galaxy Disks

1989 ◽  
Vol 134 ◽  
pp. 557-559
Author(s):  
Harding E. Smith ◽  
Ross D. Cohen ◽  
Joseph E. Burns ◽  
David J. Moore ◽  
Barbara Uchida
Keyword(s):  
Rest Frame ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Disk Galaxies ◽  
List Type ◽  
Ionization State ◽  
Low Velocity ◽  
High Ionization ◽  
Dispersion Component ◽  
Disk Component

The strong self-damped Lyman α absorption systems present in the spectra of high redshift QSOs represent a unique population of absorber which has recently been associated with the precursors of current disk galaxies. In a low resolution survey for what we have come to call “Lyman α disk systems” performed at Lick Observatory (Wolfe, et al. 1986, Ap. J. Suppl. 61, 249) approximately 18 systems with confirmed damped Lyman α profiles and rest frame equivalent widths greater than 5 Å were detected in a sample of 68 high redshift QSOs (Smith, Cohen and Bradley 1986, Ap. J. 310, 583). Subsequent higher resolution study has shown these systems to have the following properties (Turnshek, et al. 1988, Ap. J., in press): 1.Neutral hydrogen column densities, 2 × 1020 ≤ NHI ≤ 8 × 1021 cm−2.2.Low-mixed ionization state. Typically the low ionization states dominate the high ionization states (e.g. CII ≫ CIV). Some enrichment has occurred, −2≲[X/H]⊙ ≲0.3.Gas density, n ≲ 1 cm−3.4.The gas shows two components, a quiescent (disk) component, σν ≲ 10 km s−1, and a turbulent (halo) component, σν ≲ 20 km s−1. Some systems show only the low velocity dispersion component.5.At least one system intervening toward a radio QSO (Pks 0458-020) shows 21-cm absorption. The system shows multiple cloud structure with σν ≈ 6 km s−1, Ts ≈ 100 K, and structure extended over several kpc on the sky.6.There is evidence that these systems may be self gravitating with scale height of the order of 300 pc.7.These systems represent a unique population of absorber (distinct from the ‘Lyman a forest’ and heavy element systems) covering approximately 20% of the sky to z ≈ 3 and accounting for all of the baryonic matter at that redshift.

scholarly journals Warp or lag? The ionized and neutral hydrogen gas in the edge-on dwarf galaxy UGC 1281

2011 ◽  
Vol 414 (4) ◽  
pp. 3444-3457 ◽  
Author(s):  
P. Kamphuis ◽  
R. F. Peletier ◽  
P. C. van der Kruit ◽  
G. H. Heald
Keyword(s):  
Dwarf Galaxy ◽  
Neutral Hydrogen ◽  
Hydrogen Gas

Hydrogen gas re-emission from beam target bombarded by intense neutral hydrogen beam of 75–100 keV, 1.4 MW at the prototype JT-60 injector

1984 ◽  
Vol 128-129 ◽  
pp. 713-716 ◽  
Author(s):  
Takemasa Shibata ◽  
Mamoru Matsuoka ◽  
Yoshihiro Ohara ◽  
Yoshikazu Okumura ◽  
Kiyoshi Shibanuma
Keyword(s):  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Hydrogen Beam

scholarly journals Neutral Hydrogen in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 37-44
Author(s):  
L. Staveley-Smith ◽  
S. Kim ◽  
S. Stanimirović
Keyword(s):  
Atomic Hydrogen ◽  
Large Scale ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Neutral Hydrogen ◽  
Distribution Functions ◽  
Magellanic Clouds ◽  
Self Gravity ◽  
Rotational Shear ◽  
Compact Array

We review observations of neutral atomic hydrogen (HI) in the Magellanic Clouds (MCs). Being the nearest gas-rich neighbours of the Milky Way the MCs give us an excellent opportunity to study in detail the structure and evolution of the interstellar medium (ISM) and the effect of interactions between galaxies. HI in emission provides a probe of the structure and velocity field of the Clouds, allowing the study of their velocity dispersion, 3-D structure, and large-scale total-mass distribution. Recent data from Australia Telescope Compact Array surveys reveal a morphology (for both Clouds) which is heavily dominated by the effects of local star-formation, rotational shear, fragmentation, self-gravity and turbulence. The new data, which has a spatial resolution down to 10 pc, also allows the study of the distribution functions in velocity and mass for HI clouds. We discuss the morphology, dynamics and giant shell population of the LMC and SMC.

scholarly journals A Search for Low-Velocity Neutral Hydrogen in the Magellanic Stream

1984 ◽  
Vol 108 ◽  
pp. 139-140
Author(s):  
N. V. Bystrova
Keyword(s):  
Neutral Hydrogen ◽  
Velocity Range ◽  
Low Velocity ◽  
Large Velocity ◽  
Magellanic Stream

The large velocity range of the HI clouds belonging to the Magellanic Stream, as found by Haynes (1979), makes it reasonable to search for some low LSR velocity neutral hydrogen possibly belonging to the Stream. This gas, if any, would be severely blended by the local galactic gas.

scholarly journals Line Intensity Mapping during the Epoch of Reionization

2017 ◽  
Vol 12 (S333) ◽  
pp. 250-253
Author(s):  
Marta B. Silva ◽  
Saleem Zaroubi
Keyword(s):  
High Redshift ◽  
Three Dimensional ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Light Sources ◽  
First Stars ◽  
Galaxy Surveys ◽  
Gas Phases ◽  
Intensity Mapping ◽  
High Redshift Universe

AbstractCharacterizing the properties and the evolution of the first stars and galaxies is a challenging task for traditional galaxy surveys since they are sensitivity limited and can only detect the brightest light sources. Three-dimensional intensity mapping (IM) of transition lines can be a valuable alternative to study the high redshift Universe given that this technique avoids sensitivity limitation problems by measuring the overall emission of a line, with a low resolution, without resolving its sources. While 21cm line IM surveys probe neutral hydrogen gas and can, therefore, be used to probe the state of the IGM and the evolution of the ionization field during the Epoch of Reionization (EoR). IM surveys of other lines, such as CO, CII, Ly-alpha or H-alpha, can be used to probe the galaxies which emitted most of the ionizing radiation responsible for the EoR. These lines will trace the different ISM gas phases, the excitation state of this gas, its metallicity, etc. This study addresses IM of multiple transition lines and how it can be used to probe the EoR and to constrain the redshift evolution of galaxy properties.

scholarly journals Neutral hydrogen gas within and around NGC 1316

2019 ◽  
Vol 628 ◽  
pp. A122 ◽  
Author(s):  
P. Serra ◽  
F. M. Maccagni ◽  
D. Kleiner ◽  
W. J. G. de Blok ◽  
J. H. van Gorkom ◽  
...  
Keyword(s):  
Large Scale ◽  
Molecular Form ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Neutral Gas ◽  
Tidal Forces ◽  
The Galaxy ◽  
Long Tails ◽  
Stellar Body ◽  
Fornax Cluster

We present MeerKAT observations of neutral hydrogen gas (H I) in the nearby merger remnant NGC 1316 (Fornax A), the brightest member of a galaxy group which is falling into the Fornax cluster. We find H I on a variety of scales, from the galaxy centre to its large-scale environment. For the first time we detect H I at large radii (70–150 kpc in projection), mostly distributed on two long tails associated with the galaxy. Gas in the tails dominates the H I mass of NGC 1316: 7 × 108 M⊙– 14 times more than in previous observations. The total H I mass is comparable to the amount of neutral gas found inside the stellar body, mostly in molecular form. The H I tails are associated with faint optical tidal features thought to be the remnant of a galaxy merger occurred a few billion years ago. They demonstrate that the merger was gas-rich. During the merger, tidal forces pulled some gas and stars out to large radii, where we now detect them in the form of optical tails and, thanks to our new data, H I tails; while torques caused the remaining gas to flow towards the centre of the remnant, where it was converted into molecular gas and fuelled the starburst revealed by the galaxy’s stellar populations. Several of the observed properties of NGC 1316 can be reproduced by a ∼10:1 merger between a dominant, gas-poor early-type galaxy and a smaller, gas-rich spiral occurred 1–3 Gyr ago, likely followed by subsequent accretion of satellite galaxies.

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