Open AccessEmission and cooling by CO in interstellar shock waves
Author(s) -
Flower D. R.,
Gusdorf A.
Publication year - 2009
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2009.14569.x
Subject(s) - physics , shock wave , thermodynamic equilibrium , line (geometry) , steady state (chemistry) , shock (circulatory) , population , interstellar medium , limit (mathematics) , flow (mathematics) , astrophysics , atomic physics , mechanics , thermodynamics , galaxy , medicine , mathematics , demography , chemistry , sociology , mathematical analysis , geometry
We have calculated emission by CO molecules from interstellar shock waves. Two approximations have been used to determine the population densities, n J , of the rotational levels, J : steady state (∂/∂ t ≡ 0) and statistical equilibrium (d/d t ≡ 0) . A large‐velocity‐gradient approximation to the line‐transfer problem was adopted in both cases. We find that there can be substantial differences between the values of the integrated rotational line intensities calculated in steady state and in the limit of statistical equilibrium. On the other hand, although CO can be the dominant coolant towards the rear of the cooling flow which follows the dynamical heating of the gas, the rate of cooling computed assuming statistical equilibrium is likely to be reasonably accurate, given that the limit of statistical equilibrium is approached in this region.