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J. N. Bregman, E. D. Miller, J. A. Irwin (U. Michigan)
Cooling flow models for the hot gas in elliptical galaxies predict that gas is cooling at a rate of ~ 1 Msolar/yr, yet there is little evidence for this phenomenon beyond the X-ray waveband. If hot gas is cooling, it will radiate in the UV OVI lines as the gas passes through the 3EK regime. These lines 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 OVI doublet is not detected, leading to an upper limit on the cooling rate of 0.3 Msolar/yr, which is below the predicted values from the cooling flow model of 0.4-0.9 Msolar/yr. However, OVI line emission is clearly detected in NGC 4636, indicating a cooling rate of 0.65+/-0.07 Msolar/yr, which is consistent with the range of values from the cooling flow prediction, 0.36-2.3 Msolar/yr. This is the first definitive evidence outside of the X-ray waveband for the presence of a cooling flow in an elliptical galaxy. We would like to thank NASA and the FUSE team for their help and support.