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Heavy-element enrichment in low-density regions of the intergalactic medium

Nature volume 394, pages 44–46 (1998)Cite this article

Abstract

Models for the composition of the diffuse intergalactic medium1,2 predict that low-density intergalactic gas at high redshift should be very poor in heavy elements. This is because locations of early star formation (and thus of heavy-element synthesis) and of gas delivery from such stars are located preferentially within higher-density regions of the intergalactic gas. Here we present a method for analysing carbon and oxygen absorption lines in quasar spectra that allows us to probe the heavy-element abundances at a redshift of three within low-density regions of intergalactic gas. We find that the ratio of triply ionized carbon to neutral hydrogen is roughly constant over a wide range of densities, and that, even as the density approaches zero, the ratio remains high. This unexpected enrichment of low-density gas in heavy elements suggests that early generations of small galaxies might be much more efficient at ejecting heavy elements into the intergalactic medium than has previously been thought.

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Figure 2: The median τ(C IV) in 1,500-element bins (crosses) as a function of τ(Lyα).
Figure 1: Plots showing the difference between the observed distribution of τ(C IV) computed in three ranges of τ(Lyα), that is [0.5,2], [2.5] and [5,20], and the normalized distribution of τ(C IV) computed for τ(Lyα) < 0.1.

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Acknowledgements

We thank the many people at the Keck telescopes who assisted with these observations, particularly S. Vogt whose HIRES spectrograph made the observations possible. L.L.C. and A.S. are visiting astronomers at the W. M. Keck Observatory, jointly operated by the California Institute of Technology and the University of California. This work was supported by the US NSF.

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  1. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, 96822, Hawaii, USA

    Lennox L. Cowie & Antoinette Songaila

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  1. Lennox L. Cowie
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  2. Antoinette Songaila
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Correspondence to Lennox L. Cowie.

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Cowie, L., Songaila, A. Heavy-element enrichment in low-density regions of the intergalactic medium. Nature 394, 44–46 (1998). https://doi.org/10.1038/27845

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