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The FUSE Survey of 0 VI in the Galactic HaloThis paper summarizes the results of the Far-Ultraviolet Spectroscopic Explorer (FUSE) program to study 0 VI in the Milky Way halo. Spectra of 100 extragalactic objects and two distant halo stars are analyzed to obtain measures of O VI absorption along paths through the Milky Way thick disk/halo. Strong O VI absorption over the velocity range from -100 to 100 km/s reveals a widespread but highly irregular distribution of O VI, implying the existence of substantial amounts of hot gas with T approx. 3 x 10(exp 5) K in the Milky Way thick disk/halo. The overall distribution of O VI is not well described by a symmetrical plane-parallel layer of patchy O VI absorption. The simplest departure from such a model that provides a reasonable fit to the observations is a plane-parallel patchy absorbing layer with an average O VI mid-plane density of n(sub 0)(O VI) = 1.7 x 10(exp -2)/cu cm, a scale height of approx. 2.3 kpc, and a approx. 0.25 dex excess of O VI in the northern Galactic polar region. The distribution of O VI over the sky is poorly correlated with other tracers of gas in the halo, including low and intermediate velocity H I, Ha emission from the warm ionized gas at approx. l0(exp 4) K, and hot X-ray emitting gas at approx. l0(exp 6) K . The O VI has an average velocity dispersion, b approx. 60 km/s and standard deviation of 15 km/s. Thermal broadening alone cannot explain the large observed profile widths. A combination of models involving the radiative cooling of hot fountain gas, the cooling of supernova bubbles in the halo, and the turbulent mixing of warm and hot halo gases is required to explain the presence of O VI and other highly ionized atoms found in the halo. The preferential venting of hot gas from local bubbles and superbubbles into the northern Galactic polar region may explain the enhancement of O VI in the North.
Document ID
20040037730
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Sonneborn, George
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Savage, B. D.
(Wisconsin Univ.)
Wakker, B. P.
(Wisconsin Univ.)
Sembach, K. R.
(Space Telescope Science Inst. Baltimore, MD, United States)
Jenkins, E. B.
(Princeton Univ. NJ, United States)
Moos, H. W.
(Johns Hopkins Univ. Baltimore, MD, United States)
Shull, J. M.
(Colorado Univ.)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Astrophysics
Meeting Information
Meeting: IAU XXV General Assembly, Symposium No. 217
Location: Sydney
Country: Australia
Start Date: July 1, 2003
Sponsors: International Astronomical Union
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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