Sensitive mainline OH spectra of three H II regions
Abstract
The spectra of the hydroxyl mainlines in the H II regions W 49 OH, W 51 OH, and ON 1 have been observed. These OH spectra reveal the following: (1) many new, weak, narrow, non-LTE emission and absorption features, some of which are highly circularly polarized and are good candidates for a Zeeman splitting study; (2) OH within the regions forms a velocity spread of up to 120 km/s; (3) kinematic activity is most likely responsible for these OH velocity spreads; non-Doppler (scattering, etc.) explanations are unlikely; (4) there is a preponderance of OH emission maser features which are blueshifted with respect to the systemic velocity of the H II regions; (5) the intervening extended absorption features in W 49 OH at 64 and 40 km/s have small velocity widths, and are surrounded in velocity by a cluster of weaker features; the 64 km/s feature has the maximum optical depth of 0.1; and (6) the 5 km/s extended absorption feature in W 51 OH is not in LTE.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1981
- Bibcode:
- 1981A&A....96..230C
- Keywords:
-
- Astronomical Spectroscopy;
- H Ii Regions;
- Hydrogen Ions;
- Hydroxyl Emission;
- Interstellar Masers;
- Microwave Spectra;
- Angular Distribution;
- Circular Polarization;
- Electromagnetic Scattering;
- Velocity Distribution;
- Astrophysics