The origin of C IV absorption systems at redshifts z < 1: discovery of extended C IV envelopes around galaxies

We report the discovery of extended C IV gaseous envelopes around galaxies of a wide range of luminosity and morphological type. First, we show that C IV absorption systems are strongly clustered around galaxies on velocity scales of v ≲ 250 km s^-1 and impact parameter scales of ρ ≲ 100 h^-1 kpc, but not on larger velocity or impact parameter scales. Next, adopting measurements of galaxy properties presented in previous papers (which include B-band luminosity, surface brightness, and disk-to-bulge ratio), we examine how properties of the C IV absorption systems depend on properties of the galaxies. On the basis of 14 galaxy and absorber pairs and 36 galaxies that do not produce corresponding C IV absorption lines to within sensitive upper limits, we find that: (1) Galaxies of a range of morphological type and luminosity appear to possess extended C IV gaseous envelopes of radius R ≈ 100 h^-1 kpc, with abrupt boundaries between the C IV absorbing and nonabsorbing regions. (2) The extent of C IV-absorbing gas around galaxies scales with galaxy B-band luminosity as R ∝ L^0.5±0.1_B but does not depend strongly on galaxy surface brightness, redshift, or morphological type. (3) The covering factor of C IV clouds within ≈100 h^-1 kpc of galaxies is nearly unity, but there is a large scatter in the mean number of clouds encountered along the line of sight. After scaling to the luminosity of an L* galaxy, we find that 13 of 14 galaxies of impact parameter ρ < 100 h^-1 kpc are associated with corresponding C IV absorption lines, while only one of 36 galaxies of impact parameter ρ > 100 h^-1 kpc are associated with corresponding C IV absorption lines. The most significant implication of the study is that galaxies of a wide range of luminosity and morphological type are surrounded by chemically enriched gas that extends for at least ≈100 h^-1 kpc. We consider various scenarios that may have produced metals at large galactic distance and conclude that accreting satellites are most likely to be responsible for chemically enriched gas at large galactic distances to regular-looking galaxies.