The Sources of intergalactic metals

We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 Civ and 81 Siiv absorption components with N ≥ 10 12 cm -2 and 316 Mg II and 82 Fell absorption components with N ≥ 10 11.5 cm -2 in 19 high signal-to-noise ratio (60-100 pixel -1 ), high-resolution (R = 45 000) quasar spectra. C IV and Si iv trace each other closely and their line-of-sight correlation functions ξ(v) exhibit a steep decline at large separations and a flatter profile below 150 km s -1 , with a large overall bias. These features do not depend on absorber column densities, although there are hints that the overall amplitude of ξ CIV (v) increases with time over the redshift range detected (1.5-3). Carrying out a detailed smoothed particle hydrodynamic simulation (2 x 320 3 , 57 Mpc 3 comoving), we show that the C iv correlation function cannot be reproduced by models in which the IGM metallicity is constant or a local function of overdensity (Z Δ 2/3 ). However, the properties of ξ CIV (v) are generally consistent with a model in which metals are confined within bubbles with a typical radius R s about sources of mass ≥M s . We derive best-fitting values of R s 2 comoving Mpc and M s 10 12 M ○. at z = 3. Our lower-redshift (0.5-2) measurements of the Mg II and Fe II correlation functions also uncover a steep decline at large separations and a flatter profile at small separations, but the clustering is even higher than in the z = 1.5-3 measurements, and the turnover is shifted to somewhat smaller distances, 75 km s -1 . Again, these features do not change with column density, but there are hints that the amplitudes of ξ Mg II (v) and ξ Fe II (v) increase with time. We describe an analytic 'bubble' model for these species, which come from regions that are too compact to be accurately simulated numerically, deriving best-fitting values of R s 2.4 Mpc and M s 10 12 M ○. . Equally good analytic fits to all four species are found in a similarly biased high-redshift enrichment model in which metals are placed within 2.4 comoving Mpc of M s 3 x 10 9 sources at z = 7.5.