Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990a%26as...83..119c&link_type=abstract
Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 83, no. 1, April 1990, p. 119-144. Research supported by Max
Astronomy and Astrophysics
Astrophysics
205
Ammonia, H Ii Regions, Interstellar Chemistry, Molecular Clouds, Water Vapor, Infrared Spectra, Interstellar Masers, O Stars, Water Masers
Scientific paper
A sample of 84 ultracompact HII regions and sources with similar infrared colors have been surveyed in the 6(16)-5(23) H2O maser transition and in the (1,1) and (2,2) ammonia lines, using the Effelsberg 100 m telescope. Ammonia was detected in 70 percent and water in 67 percent of the sources with little obvious differentiation between sources where ultracompact HII regions are known from radio continuum measurements to be present and those for which such information is not available. Kinematic distances for the sources in the survey were derived, and it was possible in most cases to resolve the distance ambiguity for sources in the inner galaxy. The distribution of the sample in z (height above the galactic plane) is consistent with the distribution of the O-stars in the galaxy. Far-infrared luminosities for the sample were computed, and a correlation was found between ammonia line width and infrared luminosity. On the basis of the ammonia observations, kinetic temperature estimates were made for the molecular gas in the neighborhood of the ultracompact HII regions, and the correlation of gas temperature with other parameters was examined.
Cesaroni Riccardo
Churchwell Edward
Walmsley Charles Malcolm
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