THE LOW-REDSHIFT INTERGALACTIC MEDIUM AS SEEN IN ARCHIVAL LEGACY HST/STIS AND FUSE DATA

We present a comprehensive catalog of ultraviolet (HST/STIS and FUSE) absorbers in the low-redshift intergalactic medium (IGM) at z < 0.4. The catalog draws from much of the extensive literature on IGM absorption and reconciles discrepancies among several previous catalogs through a critical evaluation of all reported absorption features in light of new HST/COS data. We report on 746 Hi absorbers down to a rest-frame equivalent width of 12 m angstrom over a maximum redshift path length Delta z = 5.38. We also confirm 111 O VI absorbers, 29 C IV absorbers, and numerous absorption lines due to other metal ions. We characterize the bivariate distribution of absorbers in redshift and column density as a power law, (partial derivative N-2/partial derivative z partial derivative N) proportional to N (beta), where beta = 2.08 +/- 0.12 for O VI and beta = 1.68 +/- 0.03 for HI. Utilizing a more sophisticated accounting technique than past work, our catalog accounts for similar to 43% of the baryons: 24% +/- 2% in the photoionized Ly alpha forest and 19% +/- 2% in the warm-hot IGM as traced by OVI. We discuss the large systematic effects of various assumed metallicities and ionization states on these calculations, and we implement recent simulation results in our estimates.