SIMBAD references

We used FUSE to observe ultraviolet emission from diffuse O VI in the hot gas in the Galactic halo. By comparing our result with another, nearby observation blocked by an opaque cloud at a distance of 230 pc, we could subtract off the contribution from the Local Bubble, leading to an apparent halo intensity of I_OVI₌₄₆₈₀+570^_–660photons/cm2/s/sr. A correction for foreground extinction leads to an intrinsic intensity that could be as much as twice this value. Assuming T∼3x10⁵ K, we conclude that the electron density, n_e, is 0.01-0.02/cm3, that the thermal pressure, p/k, is 7000-10,000/cm3 K, and that the hot gas is spread over a length of 50-70 pc, implying a small filling factor for O VI-rich gas. ROSAT observations of emission at 1/4 keV in the same direction indicate that the X-rays are weaker by a factor of 1.1-4.7, depending on the foreground extinction. Simulated supernova remnants evolving in low-density gas have similar O VI to X-ray ratios when the remnant plasma is approaching collisional ionizational equilibrium and the physical structures are approaching dynamical ``middle age.'' Alternatively, the plasma can be described by a temperature power law. Assuming that the material is approximately isobaric and the length scales according to T^βdlnT, we find β=1.5±0.6 and an upper temperature cutoff of 10^{6.6(+0.3,–0.2)} K. The radiative cooling rate for the hot gas, including that which is too hot to hold O VI, is 6x10³⁸ ergs/s/kpc2. This rate implies that ∼70% of the energy produced in the disk and halo by SN and pre-SN winds is radiated by the hot gas in the halo.