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

We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of themolecular, neutral atomic, weakly ionized, and highly ionized components of theinterstellar and intergalactic material toward the quasar 3C 273. We identifyLy-beta absorption in 8 of the known intergalactic Ly-alpha absorbers along thesight line with rest-frame equivalent widths greater than 50 mA. Refinedestimates of the H I column densities and Doppler parameters (b) of the cloudsare 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 sightline 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 thatmay be associated with hot, X-ray emitting gas in the Virgo Cluster. We detectweak C III and O VI absorption in the IGM at z=0.12007; this absorber ispredominantly ionized and has N(H+)/N(H I) > 4000/Z, where Z is themetallicity. Strong Galactic interstellar O VI is present between -100 and +100km/s, with an additional high-velocity wing containing about 13% of the total OVI between +100 and +240 km/s. The broad O VI absorption wing likely traces theexpulsion of hot gas out of the Galactic disk into the halo. A limit on theamount of diffuse O VI emission present 3.5 arc minutes off the sight linecombined 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)Comment: 59 pages, 15 figures, aastex condensed format, to appear in the Nov. 10, 2001 issue of the Astrophysical Journa