The Million-Degree Interstellar Medium in Spiral Galaxies
Abstract
We searched for a million-degree interstellar medium in the disks and halos of ten spiral galaxies. The sample, observed with ROSAT, contains starbursts, galaxies harboring AGNs and quiescent galaxies. The existence of hot gas was established for seven galaxies: NGC 253, NGC 1566, NGC 3079, NGC 4258, NGC 4449, NGC 4565 and NGC 4631. With the exception of NGC 4565, these galaxies show enhanced star formation or/and host AGUs. From the derived X-ray luminosity and temperature, we calculated the density and mass of the hot gas components. For the nuclear regions of NGC 253 and NGC 3079, as well as for the hot interstellar medium along the anomalous spiral arms of NGC 4258, the densities are >~10^-2 cm^-3, while n~ 10^-3 cm^-3 for the gas in the halos of the galaxies. We discuss the findings in the framework of models describing the formation of hot interstellar medium in the disk and its outflow into the halo and compare our sample to other galaxies.
- Publication:
-
Astrophysics and Space Science
- Pub Date:
- December 1999
- DOI:
- 10.1023/A:1017042306997
- Bibcode:
- 1999Ap&SS.269..459V