scholarly journals A Sky Survey of Neutral Hydrogen at l 21 cm. III. Gas at Higher Radial Velocities

1964 ◽  
Vol 17 (1) ◽  
pp. 128 ◽  
Author(s):  
RX McGee ◽  
Janice A Milton
Keyword(s):  
Radial Velocity ◽  
Atomic Hydrogen ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Radial Velocities ◽  
Channel Spacing ◽  
Sky Survey ◽  
Half Power

Information is presented concerning the distributions of the intensity and radial velocity of atomic hydrogen gas at radial velocities away from zero. The observations were made with an aerial beam of 2?2 between half-power points and a multichannel H-line receiver of channel spacing equivalent to 7 km/s and bandwidth 38 kc/s ( 8 km/s).

HI in the Small Magellanic Cloud Re-examined

1981 ◽  
Vol 4 (2) ◽  
pp. 189-195 ◽  
Author(s):  
R. X. McGee ◽  
Lynette M. Newton
Keyword(s):  
Radial Velocity ◽  
Neutral Hydrogen ◽  
Total Content ◽  
Hii Regions ◽  
Magellanic Cloud ◽  
Hydrogen Gas ◽  
Radial Velocities ◽  
Line Of Sight ◽  
Small Magellanic Cloud

Our re-examination of the neutral hydrogen gas in the Small Magellan Cloud has led to four important results. Firstly, we find that Hindman’s (1967) total content HI map is a satisfactory representation of the gas in the line of sight. Secondly, we find that the HI gas in the SMC exists in four distinct large masses separated from one another in radial velocity by 20 to 30 km s−1. Thirdly, having made this division of the gas we show that there is good correlation between the radial velocities of HII regions, supergiant stars and HI. Finally, we believe that our observations reveal that the SMC is associated with an extremely large trailing halo of HI gas which forms the major component of the inter-cloud bridge region.

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 A New HI Ring: LGG 138

1999 ◽  
Vol 16 (1) ◽  
pp. 77-83 ◽  
Author(s):  
David G. Barnes
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Density Wave ◽  
Radial Distance ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Radial Velocities ◽  
Complete Ring ◽  
Distinct Colour ◽  
Colour Break

AbstractA complete ring of neutral hydrogen gas (HI) in the LGG 138 group of galaxies has been found. The HI mass of the ring is greater than 109, and the gas appears to be rotating with a projected circular speed of ∼200 km s−1. Two bright galaxies are enclosed by the ring, both having radial velocities consistent with membership of the group. Faint stellar emission extends to the radial distance of the HI ring, where a small but distinct colour discontinuity of between 0·05 and 0·20 magnitudes is detected. Three simple models for the formation of the system are briefly described, the most likely appearing to be a past gas-sweeping collision between one of the two bright galaxies and an outside intruder, with the colour break being partly due to an expanding density wave that is triggering star formation, and partly to a different stellar population that has been collected from the outskirts of the intruder.

scholarly journals Neutral hydrogen in the Large Magellanic Cloud

1964 ◽  
Vol 20 ◽  
pp. 289-294 ◽  
Author(s):  
R. X. McGee ◽  
Janice A. Milton
Keyword(s):  
Neutral Hydrogen ◽  
Large Magellanic Cloud ◽  
Progress Report ◽  
Magellanic Cloud ◽  
Hydrogen Gas ◽  
Radial Velocities

The neutral hydrogen gas in the Large Magellanic Cloud has been observed with the 14′.5 beam of the Parkes 210-foot telescope and the 48-channel H-line receiver. We wish to present a progress report based on computer reductions of integrated brightness and median radial velocities for some 4200 profiles. The survey is incomplete for some of the southern regions below dec. −73°. Assisting in the observations were our colleagues, M. W. Sinclair, C. J. Ohlston, and G. H. Trent and the staff at ANRAO, Parkes.

scholarly journals 21 cm Hydrogen-line Survey of the Large Magellanic Cloud. I. Stellar, Nebular, and Neutral Hydrogen Radial Velocities

1964 ◽  
Vol 17 (4) ◽  
pp. 515 ◽  
Author(s):  
RX McGee
Keyword(s):  
Neutral Hydrogen ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Hydrogen Gas ◽  
Radial Velocities ◽  
Recent Survey ◽  
Hydrogen Line ◽  
Line Survey

A recent survey of the neutral hydrogen in the Large Magellanic Cloud with a 14'�5 beam and the 48�channel H�line receiver has afforded an opportunity to compare the radial velocities of a number of optical objects with the radial velocities of the hydrogen gas in their directions.

scholarly journals A Sky Survey of Neutral Hydrogen at l 21 cm. I. The General Distribution and Motions of the Local Gas

1961 ◽  
Vol 14 (2) ◽  
pp. 260 ◽  
Author(s):  
RX McGee ◽  
JD Murray
Keyword(s):  
Neutral Hydrogen ◽  
Radial Velocities ◽  
General Distribution ◽  
Line Of Sight ◽  
Hydrogen Atoms ◽  
Sky Survey ◽  
Schematic Diagrams

A survey for neutral hydrogen of the whole sky visible from Sydney has been carried out with a multichannel H-line receiver and a 2�.2 aerial beam. A sample of the profiles obtained has been analysed to present the disposition of local hydrogen in terms of three schematic diagrams: (1) the distribution of N H, the number of hydrogen atoms in a line-of-sight column of 1 cm" section, (2) a diagram of representative line halfwidths, and (3) the observed distribution of profile peak radial velocities.

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 Neutral Hydrogen Gas in Star Forming Galaxies at z=0.24

2007 ◽  
Vol 3 (S244) ◽  
pp. 366-367 ◽  
Author(s):  
Philip Lah ◽  
Jayaram N. Chengalur ◽  
Frank H. Briggs ◽  
Matthew Colless ◽  
Roberto De Propris ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Atomic Hydrogen ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Gas Content ◽  
Star Forming ◽  
Emission Signal ◽  
Neutral Gas

AbstractWe use observations from the Giant Metrewave Radio Telescope (GMRT) to measure the atomic hydrogen gas content of star-forming galaxies at z = 0.24 (i.e. a look-backtime of ~3 Gyr). To measure the HI 21 cm emission signal we stack the signal from 121 galaxies with known optical positions and redshifts. We find an average HI mass for the galaxies of (2.26 ± 0.90) × 109 M⊙. We translate this HI measurement into a cosmic density of neutral gas at z=0.24 of Ωgas = (0.91 ± 0.42) × 10−3. This value is consistent with that estimated from damped Lyα systems around this redshift.

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.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

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