FUSE Observations of O VI Absorption in the Galactic Halo

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dc.creatorSavage, B. D.
dc.creatorSembach, K. R.
dc.creatorJenkins, E. B.
dc.creatorShull, J. M.
dc.creatorYork, D. G.
dc.creatorSonneborn, G.
dc.creatorMoos, H. W.
dc.creatorFriedman, S. D.
dc.creatorGreen, J. C.
dc.creatorOegerle, W. R.
dc.creatorBlair, W. P.
dc.creatorKruk, J. W.
dc.creatorMurphy, E. M.
dc.date2000-05-02
dc.date.accessioned2026-07-25T11:10:14Z
dc.descriptionFar-ultraviolet spectra of 11 AGNs observed by FUSE are analyzed to obtain measures of O VI 1031.93 A absorption occurring over very long paths through Milky Way halo gas. Strong O VI absorption is detected along 10 of 11 sight lines. Values of log [N(O VI) sin|b|] range from 13.80 to 14.64 with a median value of 14.21. The observations reveal the existence of a widespread but irregular distribution of O VI in the Milky Way halo. Combined with estimates of the O VI mid-plane density, n0 = 2x10^(-8) cm^(-3), from the Copernicus satellite, the FUSE observations imply an O VI exponential scale height of 2.7+/-0.4 kpc. We find that N(C IV)/N(O VI) ranges from 0.15 in the disk to 0.6 along four extragalactic sight lines. The changing ionization state of the gas from the disk to the halo is consistent with a systematic decrease in the scale heights of Si IV, C IV, N V, to O VI from ~5.1 to ~2.7 kpc. While conductive heating models can account for the highly ionized atoms at low |z|, a combination of models (and processes) appears to be required to explain the highly ionized atoms found in the halo. The greater scale heights of Si IV and C IV compared to O VI suggest that some of the Si IV and C IV in the halo is produced in turbulent mixing layers or by photoionization by hot halo stars or the extragalactic background.
dc.description8 pages, AASTeX preprint format. This paper will appear in a special issue of Astrophysical Journal Letters devoted to the first scientific results from the FUSE mission
dc.identifierhttps://arxiv.org/abs/astro-ph/0005045
dc.identifierhttp://arxiv.org/abs/astro-ph/0005045
dc.identifier.urihttps://dspace.dare.co.zw/handle/123456789/1047
dc.subjectAstrophysics
dc.titleFUSE Observations of O VI Absorption in the Galactic Halo
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