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When does the intergalactic medium become enriched?

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Original languageEnglish
Title of host publicationCRAL-2006 Chemodynamics
Subtitle of host publicationFrom First Stars to Local Galaxies
EditorsE. Emsellem, H. Wozniak, G. Massacrier, J.-F. Gonzales, J. Devriendt, N. Champavert
Pages157-162
Number of pages6
DOIs
Publication statusPublished - 30 May 2007

Publication series

NameEAS Publications Series
Volume24
ISSN (Print)1633-4760
ISSN (Electronic)1638-1963

Abstract

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 Ω(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 Civ 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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