Observations of the J = 1-0 transition of HCO/+/ in southern molecular clouds
Abstract
The J = 1-0 transition of HCO(+) at 89 GHz has been detected with the 4-m Epping radio telescope at 42 positions out of a total sample of 55 associated with dense molecular clouds (mostly with southern declinations). The telescope beamwidth was 3.3 arcmin and the sensitivity limit was 0.5-0.75 K in 'corrected antenna temperature'. The lower limit for the typical HCO(+) column density, based on assumptions of low optical depth and an excitation temperature of 15 K, is 3 x 10 to the 13th per sq cm. The velocities of the HCO(+) emission are similar to those of ground-state transitions of CO, CS, HCN; there is also a strong correlation between the HCO(+) and HCN profile areas. Extensive HCO(+) emission has been observed in the Galactic Center region, associated with a dense molecular cloud complex in the nuclear disk. Faint HCO(+) emission is presented in N159 in the Large Magellanic Cloud and possibly in NGC 5128.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 1981
- DOI:
- 10.1093/mnras/194.4.911
- Bibcode:
- 1981MNRAS.194..911B
- Keywords:
-
- Electron Transitions;
- Interstellar Gas;
- Molecular Clouds;
- Positive Ions;
- Radio Sources (Astronomy);
- Southern Sky;
- Galactic Nuclei;
- Hydrocyanic Acid;
- Ion Density (Concentration);
- Astrophysics