Magnetohydrodynamic shocks in diffuse clouds. III - The line of sight toward Zeta Ophiuchi

1986 ◽  
Vol 310 ◽  
pp. 408 ◽  
Author(s):  
B. T. Draine
Keyword(s):  
Line Of Sight ◽  
Diffuse Clouds ◽  
Magnetohydrodynamic Shocks

scholarly journals The Mass Spectrum of Interstellar Clouds

1989 ◽  
Vol 120 ◽  
pp. 511-517
Author(s):  
John M. Dickey ◽  
R. W. Garwood
Keyword(s):  
Cross Sections ◽  
Molecular Clouds ◽  
Column Density ◽  
Unit Volume ◽  
Empirical Relationship ◽  
Line Of Sight ◽  
Interstellar Clouds ◽  
Absorption Studies ◽  
Low Latitudes ◽  
Diffuse Clouds

AbstractThe abundance of 21-cm absorption lines seen in surveys at high latitudes can be translated into a line of sight abundance of clouds vs. column density using an empirical relationship between temperature and optical depth. As VLA surveys of 21-cm absorption at low latitudes are now becoming available, it is possible to study the variation of this function with galactic radius. It is interesting to compare the abundance of these diffuse atomic clouds (with temperatures of 50 to 100 K and masses of 1 to 10 M⊙) to the abundance of molecular clouds. To do the latter we must make assumptions about cloud cross-sections in order to convert the line of sight abundance of diffuse clouds into a number per unit volume, and to convert from cloud column density to mass. The spectrum of diffuse clouds matches fairly well the spectrum of molecular clouds, although observationally there is a gap of several orders of magnitude in cloud mass. Optical absorption studies also agree well with the 21-cm results for clouds of column density a few times 1020 M⊙.

scholarly journals The molecular chemistry of diffuse and translucent clouds in the line-of-sight to Sgr B2: Absorption by simple organic and inorganic molecules in the GBT PRIMOS survey

2018 ◽  
Vol 610 ◽  
pp. A10 ◽  
Author(s):  
J. F. Corby ◽  
B. A. McGuire ◽  
E. Herbst ◽  
A. J. Remijan
Keyword(s):  
Molecular Hydrogen ◽  
Galactic Center ◽  
Galactic Disk ◽  
Outer Edge ◽  
Line Of Sight ◽  
Galactocentric Distance ◽  
Molecular Chemistry ◽  
Inorganic Molecules ◽  
Diffuse Clouds ◽  
First Time

The 1–50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains ~50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of-sight material is associated with diffuse and translucent clouds located in the Galactic center, bar, and spiral arms in the disk. We measured the column densities and estimate abundances, relative to H2, of 11 molecules and additional isotopologues observed in this material. We used absorption by optically thin transitions of c-C3H2 to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H2CS, and HCS+; oxygen-bearing molecules OH, SiO, and H2CO; and simple hydrocarbon molecules c-C3H2, l-C3H, and l-C3H+. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic bar and in or near the Galactic center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C3H2/c-H13CCCH provides a good estimate of the 12C/13C ratio, whereas H2CO/H213CO exhibits fractionation. Third, we report the presence of l-C3H+ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not a simple function of AV.

scholarly journals Complex organic molecules in diffuse clouds along the line of sight to Sagittarius B2 (Corrigendum)

2018 ◽  
Vol 610 ◽  
pp. C2 ◽  
Author(s):  
V. Thiel ◽  
A. Belloche ◽  
K. M. Menten ◽  
R. T. Garrod ◽  
H. S. P. Müller
Keyword(s):  
Organic Molecules ◽  
Line Of Sight ◽  
Diffuse Clouds ◽  
Complex Organic

scholarly journals Complex organic molecules in diffuse clouds along the line of sight to Sagittarius B2

2017 ◽  
Vol 605 ◽  
pp. L6 ◽  
Author(s):  
V. Thiel ◽  
A. Belloche ◽  
K. M. Menten ◽  
R. T. Garrod ◽  
H. S. P. Müller
Keyword(s):  
Organic Molecules ◽  
Line Of Sight ◽  
Diffuse Clouds ◽  
Complex Organic

towards and within the Galactic centre

2006 ◽  
Vol 364 (1848) ◽  
pp. 3035-3042 ◽  
Author(s):  
T.R Geballe
Keyword(s):  
Rotational Level ◽  
Ionization Rate ◽  
High Resolution Spectroscopy ◽  
Line Of Sight ◽  
Galactic Centre ◽  
Long Line ◽  
Wide Range ◽  
The Galaxy ◽  
Infrared Sources ◽  
Diffuse Clouds

High-resolution spectroscopy of bright infrared sources in the centre of the Galaxy has resulted in the detection of in a remarkable array of dense and diffuse clouds along the 8000 parsec long line of sight, at a wide range of distances from the centre. Most prominent among these is a previously undetected, but very large amount of warm ( T ∼250 K) and diffuse ( n ∼100 cm 2 ) gas within a few hundred parsecs of the centre. The key to understanding the environment of the in this region is an absorption line at 3.53 μm from the metastable (3,3) rotational level, which has not been detected in dense or diffuse clouds outside of the Galactic centre (GC). We have used spectroscopy of this line along with other lines of and CO to characterize all of the clouds along the line of sight to the GC. The high abundance of in the central few hundred parsecs implies an ionization rate there that is several times larger than estimated for diffuse clouds outside the GC, and nearly two orders of magnitude greater than originally predicted for diffuse clouds.

Variation of the amount of hydrogen along the galactic ridge

1967 ◽  
Vol 31 ◽  
pp. 171-172
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Surface Brightness ◽  
Milky Way ◽  
Neutral Hydrogen ◽  
Line Of Sight ◽  
Optical Surface ◽  
Hydrogen Density ◽  
Continuous Radiation ◽  
Galactic Longitude

The integralNHof neutral-hydrogen density along the line of sight is determined from the Kootwijk and Sydney surveys. The run ofNHwith galactic longitude agrees well with that of thermal continuous radiation and that of the optical surface brightness of the Milky Way.

Structuring, Motions and Shapes of Corona Emission Line Profiles

1994 ◽  
Vol 144 ◽  
pp. 421-426
Author(s):  
N. F. Tyagun
Keyword(s):  
Emission Line ◽  
Filling Factor ◽  
Direct Relationship ◽  
Coronal Plasma ◽  
Line Of Sight ◽  
Line Profiles ◽  
The Difference ◽  
Yellow Line ◽  
Red Line

AbstractThe interrelationship of half-widths and intensities for the red, green and yellow lines is considered. This is a direct relationship for the green and yellow line and an inverse one for the red line. The difference in the relationships of half-widths and intensities for different lines appears to be due to substantially dissimilar structuring and to a set of line-of-sight motions in ”hot“ and ”cold“ corona regions.When diagnosing the coronal plasma, one cannot neglect the filling factor - each line has such a factor of its own.

HUMAN LIMITATIONS OF LINE OF SIGHT MISSILES DURING LIMITED VISIBILITY.

1968 ◽  
Author(s):  
ANDREW J. ECKLES ◽  
THOMAS A. GARRY ◽  
WILLIAM C. MULLEN
Keyword(s):  
Line Of Sight ◽  
Limited Visibility
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