The clustering of intergalactic metals

We measure the spatial clustering of metals in the intergalactic medium (IGM) from z = 1.7 to 3.0, as traced by 643 C IV and 104 Si IV N ≥ 10 ¹² cm^-2 absorption systems in 19 high signal-to-noise ratio (40-80) and high-resolution (R = 45,000) quasar spectra. The number densities and two-point correlation functions of both these species are largely constant with redshift, suggesting that the bulk of metal ejection occurred at z ≥ 3. However, at z ≤ 1.9, some additional signature appears in the C IV correlation function at 500 km s^-1, associated with four strong and peculiar systems. At all redshifts, the C IV and Si IV correlation functions exhibit a steep rise at large separations and a flatter profile at small separations, with an elbow occurring at ∼150 km s^-1. We show that these properties are consistent with metals confined within bubbles with a typical radius R_s about sources of mass ≥M_s, and we use numerical simulations to derive best-fit values of R_s ∼ 2 comoving Mpc and M_s ∼ 5 × 10¹¹ M _⊙ at z = 3. This does not exclude the possiblity that metals could have been produced at higher redshifts in smaller, but equally rare, objects. At the level of detection of this survey, IGM enrichment is likely to be incomplete and inhomogeneous, with a filling factor of ∼10%.