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Far Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption Toward 3C 273

K. R. Sembach·J. C. Howk·B. D. Savage·J. M. Shull·W. R. Oegerle
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Abstract

We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the molecular, neutral atomic, weakly ionized, and highly ionized components of the interstellar and intergalactic material toward the quasar 3C 273. We identify Ly-beta absorption in 8 of the known intergalactic Ly-alpha absorbers along the sight line with rest-frame equivalent widths greater than 50 mA. Refined estimates of the H I column densities and Doppler parameters (b) of the clouds are presented. We find a range of b = 16-46 km/s. We detect multiple H I lines (Ly-beta - Ly-theta) in the 1590 km/s Virgo absorber and estimate log N(H I) = 15.85, ten times more H I than in all of the other absorbers along the sight line combined. The Doppler width of this absorber, b ~ 16 km/s, implies T < 15,000 K. We detect O VI absorption at 1015 km/s at the 2-3 sigma level that may be associated with hot, X-ray emitting gas in the Virgo Cluster. We detect weak C III and O VI absorption in the IGM at z=0.12007; this absorber is predominantly ionized and has N(H+)/N(H I) > 4000/Z, where Z is the metallicity. Strong Galactic interstellar O VI is present between -100 and +100 km/s, with an additional high-velocity wing containing about 13% of the total O VI between +100 and +240 km/s. The broad O VI absorption wing likely traces the expulsion of hot gas out of the Galactic disk into the halo. A limit on the amount of diffuse O VI emission present 3.5 arc minutes off the sight line combined with the observed O VI column density toward 3C 273, implies n_e < 0.02 cm^-3 and P/k < 11,500 cm^-3 K for an assumed temperature of 3x10^5 K. (abbreviated version)

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K. R. Sembach, J. C. Howk, B. D. Savage, J. M. Shull, W. R. Oegerle. 2001-08-02. Far Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption Toward 3C 273. https://doi.org/10.1086/323408

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