Ammonia toward DR 21 : a weak maser in ortho-NH3 ?
Abstract
Measurements of the (J,K) = (1,1), (2,2), (3,3), and (4,4) rotation-inversion doublet lines of NH3, made with the 100-m telescope toward the thermal continuum source DR 21 are presented. The results show absorption in the (1,1) and (2,2), neither absorption nor emission in the (4,4) lines of para-NH3, and emission from the (3,3) line of ortho-NH3. The authors interpret these results in terms of deviations from LTE in the population of the (3,3) doublet. Additonal measurements of the (3,3) line with the VLA yield an upper limit of 30K to the line emission. From this the authors conclude that the deviations in the population of the (3,3) levels are small. The deviations can be caused by allowed collisions which transfer population between the (J,K) = (1,0), (2,0) or (3,0) and (3,3) levels of ortho-NH3.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1983
- Bibcode:
- 1983A&A...124..322G
- Keywords:
-
- Ammonia;
- Interstellar Masers;
- Molecular Clouds;
- Line Spectra;
- Molecular Energy Levels;
- Molecular Excitation;
- Astrophysics