The Properties of Intergalactic CIV Absorption II: Which Systems Are Associated With Galaxy Outflows?

Using the extremely high S/N quasar absorption-line sample described in the first paper of the series, we investigate which intergalactic C IV absorption line systems could be directly associated with galactic outflows at z = 2 − 3.5 from an analysis of the velocity widths of the C IV absorption line systems. Only about half the systems with a peak τ(CIV) above 0.4 in the λ1548 Å line (roughly a column density of C IV above about 2 × 10 cm) have velocity widths large enough to originate in this way, and very few of the weaker systems do. The median velocity full width at a tenth max is found to be 50 km s for systems with peak τ(CIV) in the range 0.1–0.4 and 160 km s for systems with a peak τ(CIV) in the range 0.4–3. We show that this critical value of τ(CIV) also separates systems that could be ionized by galaxy-like spectra from those in which the ionization is clearly AGN-dominated. Together the results are consistent with a picture in which almost all the lower column density, and at least half the higher column density, systems lie in the more general IGM whereas about half of the higher column density systems could be produced directly by the outflows and possibly be ionized by their parent galaxies. Subject headings: cosmology: observations — early universe — quasars: absorption lines — galaxies: evolution — galaxies: formation