The Interaction between Hot and Cold Gas in Early-Type Galaxies
Abstract
S0 and Sa galaxies have approximately equal masses of H I and X-ray emitting gas and are ideal sites for studying the interaction between hot and cold gas. An X-ray observation of the Sa galaxy NGC 1291 with the ROSAT PSPC shows a striking spatial anticorrelation between hot and cold gas where X-ray emitting material fills the large central hole in the H I disk. This supports a previous suggestion that hot gas is a bulge phenomenon and neutral hydrogen is a disk phenomenon. The X-ray luminosity (1.5 x 10^40^ ergs s^-1^) and radial surface brightness distribution (β = 0.51) is the same as for elliptical galaxies with optical luminosities and velocity dispersions like that of the bulge of NGC 1291. Modeling of the X-ray spectrum requires a component with a temperature of 0.15 keV, similar to that expected from the velocity dispersion of the stars, and with a hotter component where kT = 1.07 keV. This hotter component is not due to emission from stars and its origin remains unclear. PSPC observations are reported for the S0 NGC 4203, where a nuclear point source dominates the emission, preventing a study of the radial distribution of the hot gas relative to the H I.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/175382
- Bibcode:
- 1995ApJ...441..561B
- Keywords:
-
- Disk Galaxies;
- Elliptical Galaxies;
- Galactic Evolution;
- Gas-Gas Interactions;
- H I Regions;
- Interstellar Gas;
- X Ray Spectra;
- Astronomical Models;
- Brightness Distribution;
- Density Distribution;
- Luminosity;
- Spectrum Analysis;
- Temperature Distribution;
- Astrophysics;
- GALAXIES: ISM;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 1291;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4203;
- GALAXIES: SPIRAL;
- X-RAYS: GALAXIES