When Does the Intergalactic Medium Become Enriched?

Details When Does the Intergalactic Medium Become Enriched? When Does the Intergalactic Medium Become Enriched?

2006-10-26

arxiv.org/abs/astro-ph/0610808v1

Astronomy and Astrophysics

Astrophysics

6 pages, 3 figures, to appear in the proceedings of "Chemodynamics: from the First Stars to Local Galaxies", Lyon, France, Jul

Scientific paper

10.1051/eas:2007023

We use cosmological hydrodynamic simulations including galactic feedback based on observations of local starbursts to find a self-consistent evolutionary model capable of fitting the observations of the intergalactic metallicity history as traced by C IV between z=6.0->1.5. Our main finding is that despite the relative invariance in the measurement of Omega(C IV) as well as the column density and linewidth distributions over this range, continual feedback from star formation-driven winds are able to reproduce the observations, while an early enrichment scenario where a majority of the metals are injected into the IGM at z>6 is disfavored. The constancy of the C IV observations results from a rising IGM metallicity content balanced by a declining C IV ionization fraction due to a 1) decreasing physical densities, 2) increasing ionization background strength, and 3) metals becoming more shock-heated at lower redshift. Our models predict that ~20x more metals are injected into the IGM between z=6->2 than at z>6. We show that the median C IV absorber at z=2 traces metals injected 1 Gyr earlier indicating that the typical metals traced by C IV are neither from very early times nor from very recent feedback.

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