FUV Observations of a Strong OVI Absorber and a Lyman Limit System

• Main Authors: Lehner, N, Howk, J C, Prochaska, J X, Cooksey, K L, Kobulnicky, HA, Cales, S L, Williger, G M
• Format: Conference Proceeding
• Language: English
• ISSN: 0094-243X
• DOI: 10.1063/1.3154078

The O VI absorber at z = 0.2028 detected in the spectrum of the QSO PKS 0312-77 is the strongest discovered so far in the low redshift Universe (logN(O VI) = 14.95 plus or minus 0.05,) and is observed near a Lyman limit system (LLS). We present an analysis of these absorbers and their connection to galaxies based on a combination of FUV and NUV spectra of PKS 0312-77 obtained from FUSE and HST/STIS E140M/E230M and optical imaging and spectroscopy of galaxies in the field. Based on O I/H I and a photoionization model, we find a metallicity of 0.25 solar for the LLS, too enriched to be pristine IGM gas. We find that the gas resulting from the merger of a 0.7L* galaxy (impact parameter of 38 kpc) is the likely origin for the LLS. At -190 km/s from the LLS, another absorber is found with a supersolar metallicity. Outflow from this galaxy is likely responsible for this supersolar, fully ionized absorber. The metallicity variation is a possible evidence for poor mixing of metals on galactic structure as observed in the Milky Way halo. The origin of the strong O VI remains more enigmatic with plausible origins including an intragroup medium or a galactic corona.