Effects of shocks on the molecular composition of a dense interstellar cloud

Journal Article · Sun Jan 01 04:00:00 EST 1984 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190919· OSTI ID:5094322

Mitchell, G F

Chemical processes in a shocked interstellar molecular cloud have been studied by means of time-dependent kinetic calculations. Abundances of 113 species are followed for 10/sup 5/ yr after passage of the shocks. In all cases the initial gas density is 10/sup 4/ cm/sup -3/. This work differs from previous shock work in that (1) a more comprehensive set of high temperature reactions is used, (2) a number of new species is included, (3) the initial abundances of neutral carbon and CO are taken to be comparable, as required by recent observations, and (4) calculations have been carried out for a range of shock speeds from 5 to 20 km s/sup -1/. The shocks are found to become dissociative on a short time scale at a shock speed near 17 km s/sup -1/. Abundance profiles behind shocks of speeds 5, 10, and 15 km s/sup -1/ are presented for the species O, O/sub 2/, OH, H/sub 2/O, HO/sub 2/, H/sub 2/O/sub 2/, N, NH, NH/sub 2/, CN, HCN, C, CH, CH/sub 2/, CH/sub 3/, CH/sub 4/, C/sub 2/, C/sub 2/H/sub 2/, C/sub 2/H/sub 3/, C/sub 2/H/sub 4/, C/sub 2/H/sub 5/, C/sub 3/, C/sub 3/H, C/sub 3/H/sub 2/, HCO, H/sub 2/CO, NO, NO/sub 2/, N/sub 2/O, HNO, and OCN. Postshock abundnces of selected species for a dissociative shock of speed 17.5 km s/sup -1/ are discussed. Postshock column densities as a function of shock speed are presented for the species listed above. The molecules H/sub 2/O, H/sub 2/CO, CH/sub 2/, CH/sub 3/, CH/sub 4/, NH/sub 3/, and HCN attain very high postshock abundances for most off the range of shock speeds from 5 to 15 km s/sup -1/. The molecules CH, CN, C/sub 2/, C/sub 2/H/sub 2/, C/sub 2/H/sub 3/, C/sub 2/H/sub 4/, C/sub 2/H/sub 5/, C/sub 3/, C/sub 3/H/sub 2/, NO/sub 2/, N/sub 2/O, HO/sub 2/, and H/sub 2/O/sub 2/ reach high postshock abundances for at least part of the range of shock speeds slower than 15 km s/sup -1/.

• Research Organization: Department of Astronomy, Saint Mary's University, Halifax, Nova Scotia
• OSTI ID: 5094322
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 54:1; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COSMIC DUST
COSMIC GASES
COSMOCHEMISTRY
DUSTS
FLUIDS
GASES
INTERSTELLAR SPACE
KINETICS
REACTION KINETICS
SHOCK WAVES
SPACE