scholarly journals The distribution of atomic hydrogen in the galaxy

1958 ◽  
Vol 5 ◽  
pp. 16-22
Author(s):  
H. C. Van De Hulst
Keyword(s):  
The Netherlands ◽  
Radio Astronomy ◽  
Atomic Hydrogen ◽  
Neutral Hydrogen ◽  
The Past ◽  
The Galaxy ◽  
Inner Parts

It is my privilege to report here about the investigations of the distribution of neutral hydrogen in the Galaxy. These observations, conducted by the Netherlands Foundation for Radio Astronomy, were made at Kootwijk and reduced at the Leiden Observatory. More than a dozen persons have participated in this work during the past year. Among them are Prof. Oort and myself, but I should mention three in particular: C. A. Muller has perfected the instruments even further and has supervised the observations that were made during 24 hr a day. G. Westerhout has supervised most of the reductions at Leiden and has prepared the map and model of the outer parts of the Galaxy. M. Schmidt has unravelled the situation in the inner parts of the Galaxy, on the basis of his observations made for this purpose.

scholarly journals Observations of the Neutral Hydrogen in the Barred Spiral Galaxies NGC 3992 and NGC 4731

1983 ◽  
Vol 100 ◽  
pp. 235-236
Author(s):  
S. T. Gottesman ◽  
J. R. Ball ◽  
J. H. Hunter
Keyword(s):  
Radio Astronomy ◽  
Atomic Hydrogen ◽  
Spiral Galaxies ◽  
Neutral Hydrogen ◽  
Astronomy Observatory ◽  
Radio Astronomy Observatory ◽  
Barred Spiral Galaxies ◽  
Parameters Of Interest

We report observations of the atomic hydrogen properties of the barred spiral galaxies NGC 3992 and NGC 4731. These systems were observed in 1980 and 1981 with the VLA telescope of the National Radio Astronomy Observatory. In Table 1 we list the systemic parameters of interest.

scholarly journals Group pre-processing versus cluster ram-pressure stripping: the case of ESO156−G029

2019 ◽  
Vol 490 (1) ◽  
pp. L6-L11 ◽  
Author(s):  
Robert Džudžar ◽  
Virginia Kilborn ◽  
Chandrashekar Murugeshan ◽  
Gerhardt Meurer ◽  
Sarah M Sweet ◽  
...  
Keyword(s):  
Rapid Evolution ◽  
Neutral Hydrogen ◽  
Current Data ◽  
Cluster Galaxy ◽  
The Past ◽  
Gas Kinematics ◽  
Ram Pressure ◽  
The Galaxy ◽  
A Minor ◽  
Projected Distance

ABSTRACT We report on observations of ESO156−G029, member of a galaxy group which is positioned at the virial radius of cluster Abell 3193. ESO156−G029 is located ∼1.4 Mpc in projected distance from the brightest cluster galaxy NGC1500. We show that ESO156−G029 has disturbed gas kinematics and a highly asymmetric neutral hydrogen (H i) distribution, which are consequences of group pre-processing, and possibly of ram pressure. Based on the current data we propose a scenario in which ESO156−G029 had a minor gas-rich merger in the past and now starts to experience ram pressure. We infer that the galaxy will undergo rapid evolution once it gets closer to the cluster centre (less than 0.5 Mpc) where ram pressure is strong enough to begin stripping the H i from the galaxy.

scholarly journals Distribution and motions of HI in M31

1985 ◽  
Vol 106 ◽  
pp. 437-442
Author(s):  
E. Brinks ◽  
W. B. Burton
Keyword(s):  
High Resolution ◽  
Atomic Hydrogen ◽  
Line Of Sight ◽  
Complete Model ◽  
Previous Survey ◽  
The Past ◽  
The Galaxy ◽  
The One

It has become clear in the past few years that the distribution and kinematics of HI in M31 is far from simple. The new high-resolution survey made with the Westerbork SRT in the 21-cm line of atomic hydrogen by Brinks and Shane (1983) shows this dramatically. Along almost any line of sight through M31 two separate velocity systems are sampled. Based on a previous survey Shane (1978) and later Bajaja and Shane (1982) proposed that the extra component is due to warping of the plane of the galaxy into the direction of and crossing the line-of-sight. Roberts et al. (1978) and Whitehurst et al. (1978) emphasized that the observed profile structure ruled out confinement of the gas to a thin plane. Unwin (1983) reached a similar conclusion on the basis of his survey. The most complete model produced up until now which accounts for the two velocity systems is the one by Henderson (1979), based on the 100-m Effelsberg survey of M31 by Cram et al. (1980)

scholarly journals 6. The distribution of atomic hydrogen in the inner parts of the Galaxy

1957 ◽  
Vol 4 ◽  
pp. 37-41
Author(s):  
M. Schmidt
Keyword(s):  
Radial Velocity ◽  
Atomic Hydrogen ◽  
Galactic Centre ◽  
The Sun ◽  
The Galaxy ◽  
Latitude Distribution ◽  
Inner Parts

The determination of the distribution of hydrogen from 21-cm. observations in parts of the Galaxy, which are nearer to the centre than the sun, is seriously handicapped by the fact that the observed radial velocity of the hydrogen clouds determines only the distance to the galactic centre. So two possible values of the distance to the sun correspond to one value of the frequency. We have used as a criterion to separate the contributions from the two regions the latitude distribution of the radiation.

scholarly journals Measuring cosmic density of neutral hydrogen via stacking the DINGO-VLA data

2021 ◽  
Author(s):  
Qingxiang Chen ◽  
Martin Meyer ◽  
Attila Popping ◽  
Lister Staveley-Smith ◽  
Julia Bryant ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
Mass Measurement ◽  
Three Dimensional ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
One Dimensional ◽  
The Galaxy ◽  
Mass Assembly ◽  
The Universe ◽  
Good Agreement

Abstract We use the 21 cm emission line data from the DINGO-VLA project to study the atomic hydrogen gas H i of the Universe at redshifts z < 0.1. Results are obtained using a stacking analysis, combining the H i signals from 3622 galaxies extracted from 267 VLA pointings in the G09 field of the Galaxy and Mass Assembly Survey (GAMA). Rather than using a traditional one-dimensional spectral stacking method, a three-dimensional cubelet stacking method is used to enable deconvolution and the accurate recovery of average galaxy fluxes from this high-resolution interferometric dataset. By probing down to galactic scales, this experiment also overcomes confusion corrections that have been necessary to include in previous single dish studies. After stacking and deconvolution, we obtain a 30σ H i mass measurement from the stacked spectrum, indicating an average H i mass of ${{M_{\rm {{H}\,{I}}}}}=(1.67\pm 0.18)\times 10^{9}~{{{\rm M}_{\odot }}}$. The corresponding cosmic density of neutral atomic hydrogen is ${{\Omega _{\rm {{H}\,{I}}}}}=(0.38\pm 0.04)\times 10^{-3}$ at redshift of z = 0.051. These values are in good agreement with earlier results, implying there is no significant evolution of ΩH I at lower redshifts.

scholarly journals 40. Radio Astronomy

1970 ◽  
Vol 14 (1) ◽  
pp. 455-479 ◽  
Keyword(s):  
Radio Astronomy ◽  
Angular Resolution ◽  
Special Section ◽  
General Assembly ◽  
The Past ◽  
The Galaxy ◽  
Radio Studies ◽  
History Of ◽  
The Subject ◽  
Work Done

Radio astronomy continues to develop at explosive pace. In addition to containing many notable pieces of observational work carried out with improved sensitivity, angular resolution and spectral detail – and aided by data-handling techniques of increasing sophistication – the last three years have seen a flow of new and sometimes startling results. These are exemplified by the discovery of organic matter in the galaxy, and by the first observations pertaining to what are almost certainly neutron stars. The latter, of course, came with the dramatic discovery of pulsars, which are the subject of an Invited Discourse at this General Assembly.Following the custom of this Commission, I have asked different members to review the work done in each of the main fields. On this occasion a special section has been added on pulsars; since the announcement of their discovery in February 1968, the rate of publication within so narrow a field could scarcely have been equalled in the history of science. As in the past, radio studies of the planets are incorporated in the Report to Commission 16.

The Spin Temperature of the Interstellar Neutral Hydrogen

1969 ◽  
Vol 1 (5) ◽  
pp. 215-216 ◽  
Author(s):  
V. Radhakrishnan ◽  
J. D. Murray
Keyword(s):  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Spin Temperature ◽  
The Past ◽  
Brightness Temperatures ◽  
Direct Measurements ◽  
Absorption Studies ◽  
The Galaxy ◽  
Considerable Controversy ◽  
Emission Studies

The lack of any direct measurements on the spin temperature of the neutral hydrogen in the Galaxy has led to considerable controversy in the past. Estimates of the temperature have depended strongly on whether they are based on emission or absorption studies. The widely accepted value of 125°K based on emission studies dates back to Schmidt. He adopted this figure on the premise that the maximum observed brightness temperatures in the galactic plane were in directions of high optical depth. The brightness temperature was then equated with the spin temperature on the assumption that the temperature did not fluctuate very much in a large region around the Sun.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

The Long View of Planetary Systems

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Planetary Systems ◽  
Giant Planets ◽  
Milky Way Galaxy ◽  
Population Statistics ◽  
The Past ◽  
General Terms ◽  
The Galaxy ◽  
The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

scholarly journals The evolution of trauma care in the Netherlands over 20 years

2019 ◽  
Vol 46 (2) ◽  
pp. 329-335 ◽  
Author(s):  
Falco Hietbrink ◽  
Roderick M. Houwert ◽  
Karlijn J. P. van Wessem ◽  
Rogier K. J. Simmermacher ◽  
Geertje A. M. Govaert ◽  
...  
Keyword(s):  
The Netherlands ◽  
Trauma Care ◽  
Trauma System ◽  
Trauma Surgeon ◽  
Severely Injured ◽  
Severely Injured Patients ◽  
The Past ◽  
Level 1 ◽  
Trauma Surgeons ◽  
Injured Patients

Abstract Introduction In 1999 an inclusive trauma system was initiated in the Netherlands and a nationwide trauma registry, including all admitted trauma patients to every hospital, was started. The Dutch trauma system is run by trauma surgeons who treat both the truncal (visceral) and extremity injuries (fractures). Materials and Methods In this comprehensive review based on previous published studies, data over the past 20 years from the central region of the Netherlands (Utrecht) was evaluated. Results It is demonstrated that the initiation of the trauma systems and the governance by the trauma surgeons led to a region-wide mortality reduction of 50% and a mortality reduction for the most severely injured of 75% in the level 1 trauma centre. Furthermore, major improvements were found in terms of efficiency, demonstrating the quality of the current system and its constructs such as the type of surgeon. Due to the major reduction in mortality over the past few years, the emphasis of trauma care evaluation shifts towards functional outcome of severely injured patients. For the upcoming years, centralisation of severely injured patients should also aim at the balance between skills in primary resuscitation and surgical stabilization versus longitudinal surgical involvement. Conclusion Further centralisation to a limited number of level 1 trauma centres in the Netherlands is necessary to consolidate experience and knowledge for the trauma surgeon. The future trauma surgeon, as specialist for injured patients, should be able to provide the vast majority of trauma care in this system. For the remaining part, intramural, regional and national collaboration is essential

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