The sources of intergalactic metals

E. Scannapieco (1) , Christophe Pichon (2, 3) , B. Aracil (4) , Patrick Petitjean (2, 5) , R. J. Thacker (6) , D. Pogosyan (7) , Jacqueline Bergeron (2) , H. M. P. Couchman (8)

1 Kavli Institute for Theoretical Physics and Department of Physics, University of California
2 IAP - Institut d'Astrophysique de Paris
3 OAS - Observatoire astronomique de Strasbourg
4 Department of Astronomy, University of Massachusetts
5 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
6 Department of Physics, Engineering Physics and Astronomy, Queen's University
7 University of Alberta
8 Department of Physics and Astronomy, McMaster University

We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 CIV and 81 SiIV absorption components with N>= 10¹²cm^-2 and 316 MgII and 82 FeII absorption components with N>= 10^11.5cm^-2 in 19 high signal-to-noise ratio (60-100 pixel^-1), high-resolution (R= 45000) quasar spectra. CIV and SiIV trace each other closely and their line-of-sight correlation functions xi(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 xi_CIV (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 CIV correlation function cannot be reproduced by models in which the IGM metallicity is constant or a local function of overdensity (Z~Delta^2/3). However, the properties of xi_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~ 10¹²M_solar 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 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 xi_MgII(v) and xi_FeII(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~ 10¹²M_solar. 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 × 10⁹ sources at z= 7.5.

Domaines: Astrophysique [astro-ph]

E. Scannapieco, Christophe Pichon, B. Aracil, Patrick Petitjean, R. J. Thacker, et al.. The sources of intergalactic metals. Monthly Notices of the Royal Astronomical Society, 2006, 365, pp.615-637. ⟨10.1111/j.1365-2966.2005.09753.x⟩. ⟨hal-03785905⟩