Emission Mechanisms in X-Ray-faint Galaxies
Abstract
Hot gas dominates the emission in X-ray-luminous early-type galaxies, but in relatively X-ray-faint systems, integrated X-ray emission from discrete stellar-like sources is thought to be considerable, although the amount of the contribution is controversial. To help resolve this issue, we examine the radial X-ray surface brightness distribution of 17 X-ray-faint galaxies observed with the ROSAT HRI and PSPC. We assume that the stellar contribution follows a de Vaucouleurs law while the hot gas component follows a King β model. For some galaxies, both models fit equally well, but for a number of systems, a dual component model yields the best fit, from which upper bounds are placed on the stellar contribution. Best-fit values for the stellar contribution are inconsistent with (lower than) that suggested by Fabbiano, Gioia, & Trinchieri and estimated from the bulge of M31 but are consistent with the Forman, Jones, & Tucker estimate of the stellar fraction in X-ray-faint elliptical and S0 galaxies. Our results indicate an upper limit to discrete sources of LX/LB=1.6×1029 ergs s-1 L-1solar.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2001
- DOI:
- 10.1086/318353
- arXiv:
- arXiv:astro-ph/0010378
- Bibcode:
- 2001ApJ...547..154B
- Keywords:
-
- Galaxies: Elliptical and Lenticular;
- cD;
- Galaxies: ISM;
- Galaxies: Stellar Content;
- X-Rays: Galaxies;
- X-Rays: ISM;
- Astrophysics
- E-Print:
- 18 pages including 5 embedded Postscript figures. Accepted by the Astrophysical Journal