Heavy-element enrichment in low-density regions of the intergalactic medium.
Models for the composition of the diffuse intergalactic medium 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.
Institute for Astronomy, University of Hawaii, Honolulu 96822, USA. cowie@uhifa.ifa.hawaii.edu
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D055580:Astronomical Phenomena; D001256:Astronomy; D002244:Carbon / Q000737:chemistry; D005118:Extraterrestrial Environment; D006859:Hydrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D013057:Spectrum Analysis
D002244:Carbon; D006859:Hydrogen; D010100:Oxygen