| Issue |
EAS Publications Series
Volume 34, 2009
Astronomy in the Submillimeter and Far Infrared Domains with the Herschel Space Observatory
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|---|---|---|
| Page(s) | 151 - 161 | |
| DOI | https://doi.org/10.1051/eas:0934011 | |
| Published online | 20 December 2008 | |
L. Pagani and M. Gerin (eds)
EAS Publications Series, 34 (2009) 151-161
Physical and Chemical Processes in the Diffuse and Dense Neutral ISM
Dept. of Physics and Astronomy, San Jose State University, San Jose, CA 95192, USA
Most of the mass of the interstellar medium is in neutral phases that are heated by far-ultraviolet radiation from star forming regions. The gas, in turn, emits line radiation in the infrared and submillimeter that potentially has great diagnostic value. In this paper, we will review the physical processes (including heating, cooling, gas phase and grain surface chemistry) that give rise to this line emission and present diagnostic diagrams. We will also discuss several examples where models of neutral gas emission have been used to interpret line emission, including observations of H2O and O2 in molecular clouds and an example which points out the caution that must be used when applying the diagnostics to kiloparsec-sized regions in other galaxies.
© EAS, EDP Sciences, 2009