The Abundance of H 3 + Ions in Dense Interstellar Clouds
Abstract
Several simple relationships are written down which express the abundances of C+, He+, H3+, OH, and H2O in dense interstellar clouds as functions of the cosmic-ray ionization rate. It is argued that the primary source of OH is photodissociation of H2O by cosmic-ray induced photons. The abundance of H3+ is derived from observations of OH and predicted to be typically about 2 x 10-5 cm-3, independent of density. Lower limits of respectively 4 x 10-18 s-1 and 8 x 10-18 s-1 are obtained for the cosmic-ray ionization rates in the clouds L134 and B335. The abundances of H3+ are likely to be enhanced in regions in which the DCO+/HCO+ ratio is large.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1987
- DOI:
- 10.1086/165636
- Bibcode:
- 1987ApJ...321..383L
- Keywords:
-
- Abundance;
- Cosmic Rays;
- Gas Density;
- Hydrogen Ions;
- Ion Production Rates;
- Molecular Clouds;
- Computational Astrophysics;
- Hydroxyl Emission;
- Interstellar Chemistry;
- Interstellar Matter;
- Photodissociation;
- Astrophysics;
- COSMIC RAYS: GENERAL;
- INTERSTELLAR: ABUNDANCES;
- INTERSTELLAR: MOLECULES