The sources of intergalactic metals
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abstract
We study the clustering properties of metals in the intergalactic medium
(IGM) as traced by 619 CIV, 81 SiIV, N >= 10^12 cm^-2 and 316 MgII, and 82 FeII
N >= 10^11.5 cm^-2 absorption components in 19 high signal-to-noise (60-100 per
pixel), high resolution (R = 45000) quasar spectra. Over the redshift range
probed (1.5-3.0), CIV and SiIV trace each other closely and their line-of-sight
correlation functions 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 column depth. Carrying out a detailed SPH simulation (2 X
320^3, 57 Mpc^3 comoving), we show that this behavior can not be reproduced by
models in which the IGM metallicity is constant or a local function of density.
However, the CIV correlation function is consistent with a model in which
metals are confined within bubbles with a typical radius Rs = 2 comoving Mpc
about sources of mass >= Ms = 10^12 solar masses at z=3. Our lower redshift
(0.5-2) measurements of the MgII and FeII correlation functions also uncover a
steep decline at large separations and a flatter profile at small separations,
but the clustering is even higher, and the turn-over is shifted to ~ 75 km
s^-1. Again these features do not change with column depth. We describe an
analytical bubble model for these species, which come from regions that are too
compact to be simulated numerically, deriving best-fit values of R_s ~ 2.4 Mpc
and M_s ~ 10^12 solar masses. Equally good 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 3 x 10^9 solar mass sources at z = 7.5.
