THE CONNECTION BETWEEN A LYMAN LIMIT SYSTEM, A VERY STRONG O VI ABSORBER, AND GALAXIES AT z ∼ 0.203

With a column density log (O VI) = 14.95 +/- 0.05, the O VI absorber at z(abs) similar or equal to 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) similar or equal to 0.2026), we also identify a Lyman limit system (LLS, log N(H I) = 18.22(-0.25)(+0.19)). Combining FUV and NUV spectra of PKS 0312-77 with optical observations of galaxies in the surrounding field (15' x 32'), 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) similar or equal to -0.6, and that the LLS is nearly 100% photoionized. In contrast, the O VI-bearing gas is collisionally ionized at T similar to (3-10) x 10(5) K as derived from the high-ion ratios and profile broadenings. Our galaxy survey reveals 13 (0.3 less than or similar to L/L(*) less than or similar to 1.6) galaxies at rho < 2h(70)(1) Mpc and vertical bar delta v vertical bar less than or similar to 1100 km s(-1) 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) similar or equal to +0.15) at rho similar or equal to 38h(70)(-1) kpc. Outflow from this galaxy may also be responsible for the supersolar ([Z/H](abs) similar or equal to +0.15), fully ionized absorber at z(abs) similar or equal to 0.2018 (-190 km s(-1) from the LLS). The hot O VI absorber likely probes coronal gas about the 0.7 L(*) galaxy and/or (similar to 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.