Recent FUSE Observations of Diffuse O VI Emission in the Galactic Interstellar Medium

We present new results from our on-going survey of diffuse O VI (λ1032) emission in the interstellar medium with the Far Ultraviolet Spectroscopic Explorer (FUSE). Background observations obtained during 2005 and 2006 have yielded five new O VI detections of 3σ significance, and archival searches have revealed a sixth. Our sight lines probe the Magellanic Stream as well as low-velocity gas associated with the Galactic disk.

O VI emission centered at V_LSR = 19±13 km s^-1 is seen in one spectrum that probes a line of sight 1' from the Seyfert 1 galaxy Fairall 9, which shows strong O VI absorption at low velocities (Wakker et al. 2003). From the ratio of our emission-line intensity to the O VI column density in the low-velocity gas, we derive an electron density of 0.01 cm^-3 and a path length through the emitting gas of about 50 pc. The observed emission-line velocity and these derived properties suggest that the emitting gas is part of the corotating thick disk/halo of our Galaxy.

This work is supported by NASA contract NAS5-32985.