Mechanical heating of the interstellar medium. II - The phase properties and structural control
Abstract
This paper presents a simple model of the interstellar medium based on supernova domination and characterized by mechanical heating of H I regions and radiative cooling of the hottest material via a galactic fountain. A phase diagram of the H I material is derived and from it a feedback mechanism, based on the stability criterion for "intercloud" (i.e., T ∼ 104 K) material, is found which sets a lower limit to the mass exchange rate between the H I gas and the fountain.
A comparison is made with the solar neighborhood, and it is shown that, of the family of possible solutions within this model, only conditions close to the weak fountain limit are consistent with the observed interstellar pressure, the observed supernova rate, or with a limit imposed by the soft X-ray background. It is proposed that this result is not coincidental; suggestions are made regarding the influence of supernovae during galaxy formation on the product galaxy properties and regarding the contemporary influence of supernovae on the star-formation rate, either or both of which could bring about the apparent coincidence. These suggestions will be pursued in future investigations, but should they prove correct, the supernova rate per unit area and H I phase properties of a mature disk galaxy (or portion thereof) would depend only on elemental abundances and the H I scale height, and would follow the approximate formulae given in this paper. Finally, it is shown that the weak fountain limit of the present model is similar to the supernova-interstellar medium interaction model of McKee and Ostriker.- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1981
- DOI:
- 10.1086/158828
- Bibcode:
- 1981ApJ...245..534C
- Keywords:
-
- Gas Heating;
- Heat Balance;
- Hydrogen Clouds;
- Interstellar Matter;
- Phase Diagrams;
- Supernovae;
- Abundance;
- Gaseous Diffusion;
- Heat Transfer;
- Hydrogen Atoms;
- Kinetic Energy;
- Stellar Evolution;
- Astrophysics