The sources of intergalactic metals

E. Scannapieco, C. Pichon, B. Aracil, P. Petitjean, R. J. Thacker, D. Pogosyan, J. Bergeron, H. M.P. Couchman

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78 Scopus citations


We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 C IV and 81 Si IV absorption components with N ≥ 1012cm-2 and 316 Mg II and 82 Fe II absorption components with N ≥ 1011.5cm-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 C IV (v) increases with time over the redshift range detected (1.5-3). Carrying out a detailed smoothed particle hydrodynamic simulation (2 × 3203, 57 Mpc3 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 α Delta;2/3). However, the properties of ξ C IV(v) are generally consistent with a model in which metals are confined within bubbles with a typical radius Rs about sources of mass ≥Ms. We derive best-fitting values of R s ≈ 2 comoving Mpc and Ms % 1012 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 ξMg 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 Rs ≈ 2.4 Mpc and Ms & 1012 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 Ms ≈ 3 × 109 sources at z = 7.5.

Original languageEnglish (US)
Pages (from-to)615-637
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Jan 2006
Externally publishedYes


  • Cosmology: observations
  • Galaxies: formation
  • Intergalactic medium
  • Quasars: absorption lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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