The properties of intergalactic CIV absorption. II. Which systems are associated with galaxy outflows?

Using the extremely high signal-to-noise ratio quasar absorption-line sample described in the first paper of this 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 tau(C IV) above 0.4 in the 1548 angstrom line (roughly a column density of C IV above about 2; 10(13) cm(-2)) have velocity widths large enough to originate in this way, and very few of the weaker systems do. The median velocity full width at one-tenth maximum is found to be 50 km s(-1) for systems with peak tau(C IV) in the range 0.1-0.4 and 160 km s(-1) for systems with a peak tau(C IV) in the range 0.4-3. We show that this critical value of tau(C IV) also separates systems that could be ionized by galaxy-like spectra from those in which the ionization is clearly active galactic nucleus-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 intergalactic medium, whereas about half the higher column density systems could be produced directly by the outflows and possibly be ionized by their parent galaxies.