Thermal condensation of diffuse gas may occur spontaneously or may be induced by variations of the external conditions. Among the external conditions whose variations would induce phase transitions are the external pressure and the ionizing flux. Flash-like variations of the ionizing flux produce an increase of the electron density that enhances the cooling rate. After passing the flash, the cooling rate remains enhanced due to the inertia of the ionization, and eventually may induce a phase transition. This effect is analyzed in the context of pregalactic and interstellar medium conditions. This kind of induced condensation might play an important role in the large scale evolution of the medium, in particular, when the stimulating sources are able to induce condensation far away from them. Most of the models and numerical simulations of the star formation in disk galaxies include, as a main process, the self-propagating star formation. The relation between induced condensation and self-propagating star formation is considered.
Joint European and National Astronomical Meeting
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