The sources of intergalactic metals

Abstract

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≥ 1012 cm−2 and 316 Mg ii and 82 Fe ii absorption components with N≥ 1011.5 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 ξC 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∝Δ2/3). However, the properties of ξC 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 Rs≈ 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 ξFe 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.

How Did the IGM become Enriched?

“…• Metals are correlated with themselves and with galaxies (Adelberger et al, 2005;Pieri et al, 2006b;Scannapieco et al, 2006).…”

Cosmic distribution of highly ionized metals and their physical conditions in the EAGLE simulations

“…As mentioned above, the predictions are based on absorption systems by grouping components that are within ∆v ∼ 200 km/s (at z > 2 and ∆v ∼ 400 km/s at lower redshifts) from each other into systems of absorbers. The observed Siiv CDDFs, on the other hand, are often based on counting absorption components (e.g., Scannapieco et al 2006), or use narrower velocity windows than what we use here for identifying systems of absorbers (e.g., Danforth et al 2014). Noting that the low column density end of the observed CDDFs can be reduced by up to a factor ≈ 5 by grouping absorption components into systems of absorbers without significantly changing the high end of the CDDF (Boksenberg & Sargent 2015), the discrepancy between the predicted and observed CDDFs in the top panels of Fig.…”

The physics of the intergalactic medium

“…Searches for Mg II absorption systems are by far the most common because of their established connection to galaxies. Mg II absorber surveys were carried out by Lanzetta et al ͑1987͒, Tytler et Kirkman and Tytler, 1997b͒, at low redshifts they are associated with a warm-hot intergalactic medium ͑WHIM͒ ͑Tripp and Savage, 2000;Savage et al, 2002;Richter et al, 2004;Shull, 2005, 2008;Tripp et al, 2008͒ that Bergeron et al, 1994;Cowie et al, 1995;Songaila and Cowie, 1996;Barlow and Tytler, 1998;Cowie and Songaila, 1998;Ellison et al, 2000;Songaila, 2001Songaila, , 2005Songaila, , 2006Aracil et al, 2004;Pieri et al, 2006;Scannapieco et al, 2006b;Simcoe et al, 2006͒. Updated solar abundances useful for modeling the abundances of the metal absorption systems are provided by Grevesse and Sauval ͑1998͒, Allende Prieto et al ͑2001, 2002͒, Holweger ͑2001͒, and Asplund ͑2003͒.…”