Nonthermal OH main lines and the abundance of OH in interstellar dust clouds

Journal Article · Sat Dec 15 04:00:00 EST 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/157570· OSTI ID:5684058

Crutcher, R M

Whether OH main lines in interstellar dust clouds are thermal (thermal means that the excitation temperatures of the two transitions are equal) has been a matter of some controversy. New observations toward 3C 133, 3C 154, and position 2C demonstrate conclusively that OH main-line anomalies exist in those clouds. The anomaly /sup 0/T/sub e/ is 1--2 K. The effect of the small anomalies is often major, if line ratios are used together with the assumption of thermal main lines to derive OH optical depths and column densities, overestimates by an order of magnitude or more may result. We suggest that typically tau (OH) <1 in dust clouds, that N (OH)/A/sub v/approx. =8 x 10/sup 13/ cm/sup -2/ mag/sup -1/ (OH/Happrox. =4 x 10/sup -8/) over the range A/sub v/=0.4--7 mag, and that there is no evidence for very small-scale clumping in the spatial distribution of OH.

• Research Organization: Astronomy Department, University of Illinois
• OSTI ID: 5684058
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 234:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHEMICAL COMPOSITION
COSMIC DUST
DUSTS
ELECTROMAGNETIC RADIATION
ENERGY SPECTRA
ENERGY-LEVEL TRANSITIONS
EXCITATION
HYDROXYL RADICALS
INTERSTELLAR SPACE
MOLECULES
OPACITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
RADICALS
RADIOWAVE RADIATION
SPACE
SPECTRA