Water masers associated with compact molecular clouds and ultracompact Hii regions: The extended sample

2008 ◽  
pp. 151-154
Author(s):  
R. Cesaroni ◽  
G. Comoretto ◽  
M. Felli ◽  
F. Palla ◽  
J. Brand ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Hii Regions ◽  
Water Masers ◽  
Ultracompact Hii

scholarly journals Formaldehyde Abundances in the Dense Molecular Cores DR 21 and W 3(OH)

1987 ◽  
Vol 120 ◽  
pp. 185-186
Author(s):  
H. R. Dickel ◽  
W. M. Goss ◽  
A. H. Rots
Keyword(s):  
Radiative Transfer ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Hii Regions ◽  
Large Array ◽  
Very Large Array ◽  
Hydrogen Density ◽  
Dense Cores ◽  
Ultracompact Hii

Formaldehyde absorption has been observed with the Very Large Array in both the 6 cm and 2 cm transitions towards a number of ultracompact HII regions which are embedded in the dense cores of molecular clouds. Such data have been compared with the results of radiative transfer calculations to derive the distributions of the molecular hydrogen density and of the abundance of formaldehyde relative to molecular hydrogen. Results are presented for the sources DR 21 and W 3(OH).

scholarly journals Observations of Interstellar CH at 9 cm Wavelength

1976 ◽  
Vol 29 (3) ◽  
pp. 211 ◽  
Author(s):  
FF Gardner ◽  
BJ Robinson ◽  
MW Sinclair
Keyword(s):  
Transition Temperature ◽  
Ground State ◽  
Molecular Clouds ◽  
Hii Regions ◽  
The Galaxy ◽  
Galactic Sources

The 9 cm ground-state lines of CH have been observed in southern galactic sources, mainly HII regions. The F = 0-1 transition at 3264 MHz has been detected in emission in 16 sources; the F = 1-1 transition at 3335 MHz has been seen in absorption in 5 sources and in emission in 2 others. Where the F = 1-1 transition is in absorption the transition temperature is positive and below about 100 K. The F = 0-1 transition is generally inverted, with a transition temperature between -10 and 0 K. The column densities of CH are in the vicinity of lO'4 cm-2, slightly below those for OH but many times those for H2CO. There is no correlation between apparent optical depths of CH and those for OH or H2CO absorption. There is also no enhancement of CH in the dense molecular clouds near the centre of the Galaxy.

Fine Structure Lines in HII Regions Interacting with Molecular Clouds

1982 ◽  
pp. 73-80 ◽  
Author(s):  
D. A. Naylor ◽  
R. Emery ◽  
B. Fitton ◽  
I. Furniss ◽  
R. E. Jennings ◽  
...  
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Hii Regions ◽  
Fine Structure Lines

scholarly journals A blind survey of the 6.7 GHz methanol maser line

2002 ◽  
Vol 206 ◽  
pp. 143-146
Author(s):  
Marian Szymczak ◽  
Andrzej J. Kus ◽  
Grzegorz Hrynek
Keyword(s):  
Grid Point ◽  
Hii Regions ◽  
Triangular Grid ◽  
Average Sensitivity ◽  
Grid Pattern ◽  
Methanol Maser ◽  
Peak Flux ◽  
Maser Line ◽  
Methanol Masers ◽  
Ultracompact Hii

A blind survey for 6.7GHz methanol maser emission has been made with the 32 m Toruń radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4.4 covering a field of ∼21 deg2 at galactic longitudes 20° to 40° and galactic latitudes ±0°52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04kms−1. A total of 99 sources were detected, 28 of which were not found during previous searches of IRAS-selected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2. The nature of these sources is unclear.

scholarly journals Comparison of turbulence in HII regions and molecular clouds

1991 ◽  
Vol 147 ◽  
pp. 476-479
Author(s):  
C. R. O'Dell
Keyword(s):  
Molecular Clouds ◽  
Center Of Mass ◽  
Hii Regions ◽  
Emission Lines ◽  
General Increase ◽  
Hii Region ◽  
Velocity Relation ◽  
Common Center ◽  
The One ◽  
Kolmogorov Theory

Both the HII Regions and the Molecular Clouds show broadening of their emission lines beyond that expected from thermal motion and this is ascribed to turbulence. Turbulence in molecular clouds generally agrees with a model where the velocity of motion is determined by the Alfv én velocity.Turbulence in Galactic HII Regions and Giant Extragalactic HII Regions can also be studied by the width of the emission lines. The magnitude of the turbulent velocities in these regions are characteristically about 10 km/s. There is a general increase in turbulent velocity with the size of the HII Region, and this relation is close to but different from the one third power dependence expected from the most naive application of Kolmogorov theory. When a detailed study is conducted of each Galactic HII Region by means of the structure function, one finds that there is not agreement with Kolmogorov theory.The Size-Turbulent versus Velocity relation for Galactic HII Regions differs slightly from the better defined velocity relation for Giant Extragalactic HII Regions. This difference is probably due to the fact that the larger extragalactic objects are probably complexes of multiple individual HII Regions. There is no evidence that broadening of extragalactic HII Regions is due to motion about a common center of mass.

scholarly journals A 12CO Survey of the LMC with NANTEN

1999 ◽  
Vol 190 ◽  
pp. 61-66
Author(s):  
Y. Fukui ◽  
R. Abe ◽  
A. Hara ◽  
T. Hayakawa ◽  
S. Kato ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Cluster Formation ◽  
Hii Regions ◽  
Stellar Clusters ◽  
Giant Molecular Clouds

We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.

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