Hydrogen Chloride in OMC-1
Abstract
We present a map of Orion Molecular Cloud (OMC-1) in the HCl (1-0) transition, observed with the Caltech Submillimeter Observatory (CSO). The line was detected toward almost all observed positions. It shows two distinct features, a ubiquitous narrow component, associated with the quiescent dense ridge and a broad component in the vicinity of IRc2, but associated with the outflow or plateau rather than with the hot core. An excitation analysis showed that the HCl line traces very dense (greater than 107/cc) gas. The fractional HCl abundance is constant within the errors (a few x 10-10 and shows neither variation with position nor between the two components. As a result, HCl is found not to be a significant coolant of the gas. The nondetection of a hot core component may be due to a low contrast between HCl excitation temperature and effective dust temperature and probably not to a low abundance in the hot core. The chemistry of HCl was reinvestigated, and it was found that HCl contains about one-third of the available gas phase chlorine, under the conditions in OMC-1. An upper limit to the chlorine depletion of 230 +/- 80 was determined.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/175358
- Bibcode:
- 1995ApJ...441..334S
- Keywords:
-
- Astronomical Models;
- Emission Spectra;
- Hydrogen Chlorides;
- Line Spectra;
- Molecular Clouds;
- Orion Nebula;
- Astronomical Spectroscopy;
- Chemical Analysis;
- Chlorine;
- Gas Temperature;
- Interstellar Matter;
- Astrophysics;
- ISM: ABUNDANCES;
- ISM: INDIVIDUAL ALPHANUMERIC: OMC-1;
- ISM: MOLECULES;
- MOLECULAR PROCESSES