The Detection of a Cooling Flow Elliptical Galaxy from O VI Emission
Abstract
Cooling flow models for the hot gas in elliptical galaxies predict that gas is cooling at a rate of ~1 Msolar yr-1, yet there is little evidence for this phenomenon beyond the X-ray wave band. If hot gas is cooling, it will pass through the 3×105 K regime and radiate in the O VI λλ1032, 1038 ultraviolet lines, which can be detected with the Far-Ultraviolet Spectroscopic Explorer (FUSE), and here we report on FUSE observations of the X-ray bright early-type galaxies NGC 1404 and NGC 4636. In NGC 1404, the O VI doublet is not detected, implying a cooling rate less than 0.3 Msolar yr-1, which is below the predicted values from the cooling flow model of 0.4-0.9 Msolar yr-1. In NGC 4636, both O VI lines are clearly detected, indicating a cooling rate of 0.43+/-0.06 Msolar yr-1, which falls within the range of values from the cooling flow prediction, 0.36-2.3 Msolar yr-1, and is closest to the model where the production of the cooled gas is distributed through the galaxy. The emission-line widths, 44+/-15 km s-1, are close to the Doppler broadening value (30 km s-1), indicating that the flow is quiescent rather than turbulent and that the flow velocity is less than 30 km s-1.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2001
- DOI:
- 10.1086/320675
- arXiv:
- arXiv:astro-ph/0104317
- Bibcode:
- 2001ApJ...553L.125B
- Keywords:
-
- Galaxies: Individual: NGC Number: NGC 1404;
- Galaxies: Individual: NGC Number: NGC 4636;
- Galaxies: ISM;
- Astrophysics
- E-Print:
- to be published in ApJ Letters