X-Ray--emitting Gas Surrounding the Spiral Galaxy NGC 891
Abstract
We observed the edge-on spiral galaxy NGC 891 with the Position Sensitive Proportional Counter on ROSAT to search for hot extraplanar gas expected in the galactic fountain model. Diffuse X-ray emission surrounds the disk with a HWHM for the surface brightness perpendicular to the disk of 50" (2.4 kpc) and a radial extent of approximately 6.5 kpc, both of which are similar in extent to the extended Hα and radio halo component; the implied density scale height for the hot gas is 7 kpc. The spectrum is best fitted with a hard stellar component and a soft diffuse gas component of temperature 3.6 x 10^6^ K. The density of this gas is 2 x 10^-3^ cm^-3^, the luminosity is 4.4 x 10^39^ ergs s^-1^, the mass is 1 x 10^8^ M_sun_, and the pressure (P/k) is 1.4 x 10^4^ K cm^-3^. These data are consistent with this gas participating in a galactic fountain, where the material approaches hydrostatic equilibrium before cooling at a rate of 0.12 M_sun_ yr^-1^. The cooled material may be responsible for some of the Hα emission.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1994
- DOI:
- 10.1086/173587
- Bibcode:
- 1994ApJ...420..570B
- Keywords:
-
- Astronomical Models;
- Interstellar Gas;
- Spiral Galaxies;
- X Ray Spectra;
- H Alpha Line;
- High Temperature Gases;
- Pressure Effects;
- Spatial Distribution;
- Stellar Luminosity;
- Stellar Mass;
- Astronomy;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 891;
- GALAXIES: ISM;
- GALAXIES: SPIRAL;
- X-RAYS: GALAXIES