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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}_{-660} photons/cm^2/s/sr. A correction for foreground extinction leads to an intrinsic intensity that could be as much as twice this value. Assuming T ~ 3 x 10^5 K, we conclude that the electron density, n_e, is 0.01-0.02 /cm^3, the thermal pressure, p/k, is 7000-10,000 K/cm^3, 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 to 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 ioinizational 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^(beta) d(ln T), we find beta = 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 6 x 10^{38} erg/s/kpc^2. 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.
A significant fraction of baryons in galaxies are in the form of diffuse gas of the circumgalactic medium (CGM). One critical component of the multi-phases of CGM, the so-called coronal warm-hot phase gas ($rm 10^{5}-10^{6}$ K) traced by O VI 1031.93
FUSE spectra of 100 extragalactic objects are analyzed to obtain measures of O VI absorption along paths through the Milky Way thick disk/halo. Strong O VI absorption over the approximate velocity range from -100 to 100 km/s reveals a widespread but
Opacity is a property of many plasmas, and it is normally expected that if an emission line in a plasma becomes optically thick, its intensity ratio to that of another transition that remains optically thin should decrease. However, radiative transfe
We study the behaviors of galactic disks in triaxial halos both numerically and analytically to see if warps can be excited and sustained in triaxial potentials. We consider the following two scenarios: 1) galactic disks that are initially tilted rel
We have performed the largest ever particle simulation of a Milky Way-sized dark matter halo, and present the most comprehensive convergence study for an individual dark matter halo carried out thus far. We have also simulated a sample of 6 ultra-hig