scholarly journals Study of the filament WB 673 in ammonia radiolines

2021 ◽  
Author(s):  
O. L. Ryabukhina ◽  
◽  
M. S. Kirsanova ◽  
Keyword(s):  
Hyperfine Structure ◽  
Molecular Cloud ◽  
Column Density ◽  
Kinetic Temperature ◽  
Giant Molecular Cloud ◽  
Integrated Intensities

We study the molecular filament WB 673 which is located at a distance of 1.8 kpc in the giant molecular cloud G174 + 2.5. Observations of ammonia radiolines NH3 (1,1), (2,2) and (3,3) were carried out in 2019 at the Effelsberg observatory (Germany). The parameters of the lines were determined, maps of the integrated intensities of ammonia in dense clumps WB 668, WB 673, S233-IR and G173.57+2.43 were obtained. The column density of ammonia and the kinetic temperature of the gas were obtained. An analysis of the hyperfine structure anomalies of the NH3 (1,1) lines was carried out.

scholarly journals Detection of New Ammonia Sources

1980 ◽  
Vol 87 ◽  
pp. 83-84
Author(s):  
G.H. Macdonald ◽  
A.T. Brown ◽  
L.T. Little ◽  
D.N. Matheson ◽  
M. Felli
Keyword(s):  
Hyperfine Structure ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Column Density ◽  
Rotational Temperature ◽  
Kinetic Temperature ◽  
Excitation Temperature ◽  
Hydrogen Density

Ammonia is a favoured molecule for the study of molecular clouds since several important parameters of the cloud can be deduced from simple observations of the J,K=1,1 and 2,2 inversion doublet transitions and the hyperfine structure in the (1,1) line. With the additional knowledge of the kinetic temperature Tk from observations of CO, for example, it is possible to compute the excitation temperature of the (1,1) line (T11), the rotational temperature between the (1,1) and (2,2) levels (T21), the molecular hydrogen density n(H2) and ammonia column density N(NH3) (see, for example, Martin and Barrett, 1978).

scholarly journals Fine Structure of Shocked Photodissociation Regions in the Orion Bright Bar

1994 ◽  
Vol 140 ◽  
pp. 249-250
Author(s):  
Toshihiro Omodaka ◽  
Yasuhiro Murata ◽  
Masahiko Hayashi ◽  
Yoshimi Kitamura ◽  
Masatoshi Ohishi
Keyword(s):  
Shock Wave ◽  
Fine Structure ◽  
Molecular Cloud ◽  
Column Density ◽  
Ionization Front ◽  
Molecular Gas ◽  
Hii Region ◽  
Fine Structures ◽  
Photodissociation Regions ◽  
Integrated Intensities

The Orion bright bar is a prominent ionization front located approximately 2’ southeast of the Trapezium stars. Because this ionization front is seen almost edge-on, it provides an opportunity to study the interaction between the HII region and the adjacent molecular cloud. The molecular bar has been thought to be a narrow layer of ~ 50” (0.1 pc) in width parallel to the ionization front with enhanced temperature, density and column density. The molecular gas outside the ionization front was redshifted with respect to the ambient molecular cloud by 1-2 kms−1 (Omodaka et al. 1984, 1986, 1992), suggesting that the expanding HII region generated by the Trapezium stars had driven a shock wave into the molecular cloud at the southeast of the bar. This layer is exposed to intense UV radiation from the Trapezium stars, resulting in the formation of photodissociated regions.We have made aperture synthesis observations of CS(J=1-0) line and 49 GHz continuum in the Orion bright bar with the Nobeyama Millimeter Array. Figure 1, a map of integrated intensities of CS, clearly revealed fine structures of the molecular bar and more than six prominent features are confirmed. It is noted that these features are lined up at 30” from the ionization front inside the molecular cloud.

scholarly journals Supernova remnants and OH (1720 MHz) masers

2002 ◽  
Vol 206 ◽  
pp. 204-211
Author(s):  
Anne J. Green
Keyword(s):  
Molecular Cloud ◽  
Supernova Remnants ◽  
Column Density ◽  
Narrow Range ◽  
Direct Interaction ◽  
Zeeman Splitting ◽  
Volume Density ◽  
The Other ◽  
Kinetic Temperature ◽  
Satellite Line

Anomalous OH masers were detected towards supernova remnants (SNRs) more than 30 years ago. The satellite line at 1720 MHz was detected in emission, while the main lines (1665 and 1667 MHz) and the other satellite line, at 1612 MHz, occurred only in absorption. Independently, 25 years ago, a theoretical model was proposed whereby 1720 MHz OH masers could be collisionally excited by the passage of a shock through a molecular cloud. For an efficient inversion of the 1720 MHz transition, the gas should have a narrow range of physical properties, namely a kinetic temperature 50 ≤ TK ≤ 125 K, a volume density nH2 ∼ 105 cm−3, and a column density of OH gas 1016–1017 cm−2. However, it was not until 1994, with interferometric observations, that the importance of studies of these masers, formed when an SNR is in direct interaction with a molecular cloud, was realised. This discovery triggered a series of surveys to search all known Galactic SNRs. I will review the outcomes of these surveys and discuss the consequences of using 1720 MHz masers as a diagnostic tool for calculating shocked gas conditions, for magnetic field determinations (from Zeeman splitting measurements) and for measuring the properties of SNRs.

scholarly journals The low cosmic-ray density in the Polaris Flare

2021 ◽  
Vol 21 (10) ◽  
pp. 246
Author(s):  
Zhi-Wei Cui ◽  
Rui-Zhi Yang ◽  
Bing Liu
Keyword(s):  
Molecular Cloud ◽  
Molecular Clouds ◽  
Column Density ◽  
Galactic Plane ◽  
Cosmic Ray ◽  
Giant Molecular Cloud ◽  
Large Gradient ◽  
Ray Density ◽  
Density Map

Abstract We reported the γ-ray observation towards the giant molecular cloud Polaris Flare. Together with the dust column density map, we derived the cosmic ray (CR) density and spectrum in this cloud. Compared with the CR measured locally, the CR density in the Polaris Flare is significantly lower and the spectrum is softer. Such a different CR spectrum reveals either a rather large gradient of CR distribution in the direction perpendicular to the Galactic plane or a suppression of CR inside molecular clouds.

scholarly journals STAR FORMATION AND YOUNG STELLAR CONTENT IN THE W3 GIANT MOLECULAR CLOUD

2011 ◽  
Vol 743 (1) ◽  
pp. 39 ◽  
Author(s):  
Alana Rivera-Ingraham ◽  
Peter G. Martin ◽  
Danae Polychroni ◽  
Toby J. T. Moore
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Stellar Content ◽  
Giant Molecular Cloud

scholarly journals Massive stars in the giant molecular cloud G23.3−0.3 and W41

2014 ◽  
Vol 569 ◽  
pp. A20 ◽  
Author(s):  
Maria Messineo ◽  
Karl M. Menten ◽  
Donald F. Figer ◽  
Ben Davies ◽  
J. Simon Clark ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Massive Stars ◽  
Giant Molecular Cloud
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