Instabilities in Photoionized Interstellar Gas
1995; IOP Publishing; Volume: 447; Linguagem: Inglês
10.1086/175911
ISSN1538-4357
Autores Tópico(s)Spectroscopy and Laser Applications
Resumoview Abstract Citations (23) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Instabilities in Photoionized Interstellar Gas Corbelli, Edvige ; Ferrara, Andrea Abstract We present a linear analysis of acoustic and thermo-reactive instabilities in a diffuse gas, photoionized and heated by a radiation field, cooled by collisional excitation of hydrogen and metal lines. The hydrogen recombination reaction has a stabilizing effect on the thermal mode found by Field (1965) since the condensation instability occurs in a narrower region of the parameter space and grows on- longer timescales due to its oscillatory character. This effect is stronger when the mean photon energy is not much larger than the hydrogen ionization energy. Moreover, for fixed values of thermal pressure and photoionization rate, there are thermo-reactive unstable equilibria for which no transition to a stable phase is possible. By extending our analysis of the thermo-reactive modes to the nonlinear regime we show that when no phase transition is possible the medium evolves through a series of nonequilibrium states characterized by large amplitude, nonlinear periodic oscillations of temperature, density and hydrogen ionization fraction. We find also unstable acoustic waves which, for solar metal abundances, are the fastest growing modes in two temperature intervals: around T ∼ 100 K and T ∼ 8000 K (i.e., cold and warm phase, respectively), independent of the mean photon energy. Possible implications of the interstellar medium and intergalactic medium are briefly outlined. Publication: The Astrophysical Journal Pub Date: July 1995 DOI: 10.1086/175911 arXiv: arXiv:astro-ph/9503080 Bibcode: 1995ApJ...447..708C Keywords: INSTABILITIES; ISM: GENERAL; WAVES; Astrophysics E-Print: TeX file, 24 pages, 6 figures available upon request from edvige@arcetri.astro.it, to appear in The Astrophysical J. (July 10) full text sources arXiv | ADS |
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