Fast Molecular Shocks. I. Re-formation of Molecules behind a Dissociative Shock
Abstract
The physical and chemical processes that operate in the cooling gas behind a fast, dissociative, single-fluid shock propagating in a dense interstellar cloud are discussed. The treatment extends previous theoretical work on fast molecular shocks by including the effects of the conversion of Ly-alpha photons into radiation of the two-photon continuum and into H2 Lyman band emission lines, the effects of CO photodissociation following line absorption, and the formation and destruction of molecules containing the elements nitrogen, silicon, and sulphur, and of the complex hydrocarbons. Abundance profiles for the molecular species of interest are presented. After molecular hydrogen begins to reform, by means of gas phase and grain surface processes, the neutral species OH, H2O, O2, CO, CN, HCN, N2, NO, SO, and SiO reach substantial abundances. The molecular ions HeH(+), OH(+), SO(+), CH(+), H2(+), and H3(+), are produced while the gas is still hot and partially ionized. Emissions from them provide a possible diagnostic probe of fast molecular shocks.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1989
- DOI:
- 10.1086/167441
- Bibcode:
- 1989ApJ...340..869N
- Keywords:
-
- Dissociation;
- Interstellar Chemistry;
- Interstellar Matter;
- Molecular Gases;
- Shock Waves;
- Abundance;
- Gas Cooling;
- Interstellar Magnetic Fields;
- Lyman Alpha Radiation;
- Molecular Ions;
- Radiative Transfer;
- Astrophysics;
- INTERSTELLAR: MOLECULES;
- MOLECULAR PROCESSES;
- SHOCK WAVES