Photospheric Abundances of the Hot Stars in NGC 1399 and Limits on the Fornax Cluster Cooling Flow
Abstract
We present far-UV spectroscopy of the giant elliptical galaxy NGC 1399, obtained with the Far Ultraviolet Spectroscopic Explorer. Of all quiescent ellipticals, NGC 1399 has the strongest known ``UV upturn''-a sharp spectral rise shortward of 2500 Å. It is now well established that this emission comes from hot horizontal branch stars and their progeny; however, the chemical composition of these stars has been the subject of a longstanding debate. For the first time in observations of any elliptical galaxy, our spectra clearly show photospheric metallic absorption lines within the UV upturn. The abundance of N is at 45% solar, Si is at 13% solar, and C is at 2% solar. Such abundance anomalies are a natural consequence of gravitational diffusion. These photospheric abundances fall in the range observed for subdwarf B stars of the Galactic field. Although NGC 1399 is at the center of the Fornax Cluster, we find no evidence for O VI cooling flow emission. The upper limit to λλ1032, 1038 emission is 3.9×10-15 ergs s-1 cm-2, equivalent to 0.14 Msolar yr-1 and less than the value predicted by simple cooling flow models of the NGC 1399 X-ray luminosity.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2002
- DOI:
- 10.1086/340142
- arXiv:
- arXiv:astro-ph/0202212
- Bibcode:
- 2002ApJ...568L..19B
- Keywords:
-
- Galaxies: Abundances;
- Galaxies: Elliptical and Lenticular;
- cD;
- Galaxies: Stellar Content;
- Ultraviolet: Galaxies;
- Astrophysics
- E-Print:
- 4 pages, Latex. 2 figures. Uses corrected version of emulateapj.sty and apjfonts.sty (included). Accepted for publication in ApJ Letters. Revised figure placement