2009ApJ...694..734L

With a column density log N(O VI) = 14.95±0.05, the O VI absorber at z_abs≃ 0.2028 observed toward the quasi-stellar object PKS 0312-77 (z_em= 0.223) is the strongest yet detected at z < 0.5. At nearly identical redshift (z_abs≃ 0.2026), we also identify a Lyman limit system (LLS, log N(H I) = 18.22^+0.19_–0.25). Combining FUV and NUV spectra of PKS 0312-77 with optical observations of galaxies in the surrounding field (15'x32'), we present an analysis of these absorbers and their connection to galaxies. The observed O I/H I ratio and photoionization modeling of other low ions indicate that the metallicity of the LLS is [Z/H]_LLS≃ -0.6, and that the LLS is nearly 100% photoionized. In contrast, the O VI-bearing gas is collisionally ionized at T ∼ (3-10)x10⁵ K as derived from the high-ion ratios and profile broadenings. Our galaxy survey reveals 13 (0.3 ≲ L/L _*≲ 1.6) galaxies at ρ < 2h.^–1₇₀ Mpc and|δv| ≲ 1100 km/s from the LLS. A probable origin for the LLS is debris from a galaxy merger, which led to a 0.7 L_* galaxy ([Z/H]_gal≃ +0.15) at ρ ≃ 38h.^–1₇₀kpc. Outflow from this galaxy may also be responsible for the supersolar ([Z/H]_abs≃ +0.15), fully ionized absorber at z_abs≃ 0.2018 (-190 km/s from the LLS). The hot O VI absorber likely probes coronal gas about the 0.7 L_* galaxy and/or (∼0.1 keV) intragroup gas of a spiral-rich system. The association of other strong O VI absorbers with LLS suggests that they trace galactic and not intergalactic structures.