ar X iv : a st ro - p h / 00 08 14 9 v 1 9 A ug 2 00 0 Theoretical Models of Photodissociation Fronts
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چکیده
Observations of H2 line emission have revealed higher-than-expected gas temperatures in a number of photodissociation fronts. We discuss the heating and cooling processes in photodissociation regions. Observations of NGC 2023 are compared to a theoretical model in which there is substantial gas at temperatures T = 500− 1000K heated by photoelectric emission and collisional deexcitation of H2. In general the model successfully reproduces the observed H2 line emission from a wide range of energy levels. The observed [SiII]34.8μm emission appears to indicate substantial depletion of Si in NGC 2023.
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تاریخ انتشار 2000