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[143.13] Extreme Ultraviolet Spectroscopy of OIII, OIV, OV, and OVI Absorption Associated with the Quasar HE 0226-4110

R. Ganguly, K. R. Sembach (Space Telescope Science Institute), T. M. Tripp (University of Massachusetts), B. D. Savage, B. P. Wakker (University of Wisconsin)

We present FUSE and HST/STIS observations of the absorber near the emission redshift of the radio-quiet, X-ray bright quasar HE0226-4110 (z=0.495). The spectra cover the rest-frame wavelength range of 610-1140A, and we detect a wide range of ionization species in the ejection velocity range 300-700 km/s, including four adjacent stages of oxygen: OIII, OIV, OV, and OVI. Strong transitions of OI and OII are covered in our spectra, but no lines of these two species are detected. Comparison of the OVI 1031A and 1037A lines reveal no evidence for partial coverage or unresolved saturated structure, although parts of the OVI 1037A line are blended with Galactic CIV absorption. The kinematics of OV and OVI trace each other, appearing mostly in two broad components (velocity widths of 48 km/s and 72 km/s). OIII is detected only in a narrow component at an ejection velocity of 500 km/s with a velocity width of 8 km/s. This narrow component is also detected in HI, CIII, NIV, OIV, SIV, and possibly NeVIII. The kinematics of OIV, however, are more complex, and indicate that OIV traces both low- and high-ionization gas. In particular, there is an apparent velocity offset of about 10 km/s between the peaks of the OIV and OIII apparent column density profile. Preliminary comparisons of the OIII and OIV column densities in the narrow component yield a constraint on the photoionization parameter, U~0.005. At this ionization level, the HI column density implies a total hydrogen column density of 1.2e+17 cm^-2 with a metallicity of [O/H]=+0.5 for the narrow component detected in OIII. If the gas has a density of 3000 cm^-3, then the absorbing structure has a line-of-sight thickness of a few AU and lies within the host galaxy (15 kpc from the central engine).

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.