What determines the physical quantities of galaxies? A two-component gas model for protogalaxies with energy input from supernovae

概要

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The equilibrium structure of a protogalaxy, which is assumed to be composed of cold clouds and hot ambient gas in pressure equilibrium, is examined. The underlying characteristic time scales are the free-fall time of the system and the cooling time of the hot ambient gas. The global collapse condition used here is the well-known condition that the cooling time must be less than the free-fall time. Feedback processes are incorporated into the model via an energy balance condition between the power injected from supernovae and related processes due to the evolution of newly formed massive stars and the luminosity radiated by cooling processes. These considerations allow calculation of the characteristic mass and size of these two-component protogalaxies that can be expressed in terms of fundamental constants with some additional reasonably well constrained parameters. In addition, the pressure-equilibrium condition for protogalaxies with such a two-component interstellar medium indicates a characteristic mass for clouds, which is roughly comparable to the mass scale of globular clusters depending on the relevant cooling mechanism. The physical properties derived here for these protogalactic systems could be useful in interpreting high-redshift objects that may be possibly associated with galaxy formation.
American Astronomical Societyの論文
1991-06-10