Molecules, grains, and shocks - A comparison of CO, H I, and IRAS data
C. Heiles, W. T. Reach, B. C. Koo;
ApJ, 1988, 332, 313
ABSTRACT:The IR and H I properties and CO content of a set of 26 isolated, roughly degree-sized interstellar clouds are compared. It is argued that G230.1-28.4, the
cloud with the narrowest H I line, has recently been shocked by the same
collision that a neighboring cloud, G228.0-28.6, is currently undergoing.
The ratio S(100)/N(H I) is found to range up to much larger values than predicted
theoretically, where N(H) represents the column density of H nuclei and S(100) is the
100 micron surface brightness.
Clouds with the highest such values are
observed to contain CO, and it is inferred that they contain H2.
The (H2/H I) ratio of a cloud increases as the measure of its internal velocity
differences decreases. The dependence of S(60)/S(100) on V(LSR) implies that
fast shocks preferentially destroy large grains or produce small grains,
or both.
KEYWORDS: carbon monoxide, h i regions, infrared astronomy, interstellar matter, molecular clouds, particle size distribution, radio emission, shock waves, brightness, infrared astronomy satellite, interstellar gas, interstellar radiation, normal density functions
CODE: heiles88a