[ITAL]Far-Ultraviolet Spectroscopic Explorer[/ITAL] Detection of Diffuse Galactic O [CSC]vi[/CSC] Emission toward the Coma and Virgo Clusters

We report the detection of diffuse O VI 1032, 1038 A emission in a 29-ksecobservation centered on the Coma Cluster (l = 57.6, b = +88.0) and an 11-ksecobservation toward Virgo (l = 284.2, b = +74.5) through the low-resolution(30"x30") aperture of the Far Ultraviolet Spectroscopic Explorer (FUSE). Theemission lines have a redshift near zero and are thus produced by gas in ourown Galaxy. Observed surface brightnesses are 2000 +/- 600 photons/cm2/s/sr foreach of the O VI components in the Coma spectrum and 2900 +/- 700 and 1700 +/-700 photons/cm2/s/sr for the 1032 and 1038 A lines, respectively, toward Virgo.These features are similar in strength to those recently observed in thesouthern Galactic hemisphere (l = 315.0, b =-41.3) in an ~ 200 ksec FUSEobservation. From a FUSE spectrum of M87, we find that N(O VI) toward Virgo is(1.4 +/- 0.8) x 10^14 cm^{-2}. By combining emission- and absorption-line datafor this sight line, we estimate the physical parameters of the emitting gas.Comment: To appear in the Astrophysical Journal (Letters). 4 pages with 1 embedded postscript figure; uses emulateapj5.st