The low-redshift intergalactic medium as seen in archival legacy Hubble/STIS and FUSE data

TL;DR

This paper compiles and analyzes a comprehensive catalog of low-redshift intergalactic medium absorbers from Hubble and FUSE data, quantifying baryon content and absorber distributions with improved methods.

Contribution

It provides a reconciled, extensive catalog of IGM absorbers at z<0.4, with refined baryon estimates accounting for systematic effects and recent simulations.

Findings

746 HI absorbers identified down to 12 mA

43% of baryons accounted for in the low-redshift IGM

Power-law distribution of absorber line frequency with respect to column density

Abstract

We present a comprehensive catalog of ultraviolet HST/STIS and FUSE absorbers in the low-redshift IGM at z<0.4. The catalog draws from the extensive literature on IGM absorption, and it reconciles discrepancies among 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 milliAngstroms over a maximum redshift path length Deltaz=5.38. We also confirm 111 OVI absorbers, 29 CIV absorbers, and numerous absorption features due to other metal ions. We characterize the distribution of absorber line frequency as a function of column density as a power law, dN/dz \propto N^{-beta}, where beta=2.08+-0.12 for OVI and beta=1.68+-0.03 for HI. Utilizing a more sophisticated accounting technique than past work, the catalog accounts for ~43% of the baryons: 24+-2% in the photoionized Ly-alpha forest and 19+-2% in the WHIM 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.