Heavy Element Enrichment in Low
Density Regions of the IGM

Lennox L. Cowie & Antoinette Songaila

(Nature 394, 44, 1998)

Paper (revised draft, 4/1/98)
Figure 1
Figure 2
Stacking method plots
Pregalactic enrichment models for the diffuse intergalactic medium predict that at low cosmological overdensities the intergalactic gas at high redshift should be very poor in heavy elements. This is a simple consequence of the star formation and gas return mechanisms being preferentially located in the higher overdensity regions of the cosmological fluid. We present a new method of analyzing carbon and oxygen absorption lines in quasar spectra that allows us to probe the heavy element abundances at a redshift of three to much lower intergalactic densities than has been previously attempted. We find that the ratio of triply ionized carbon to neutral hydrogen (C IV/H I) remains roughly constant over a wide range of overdensities and that even as the overdensity approaches zero the ratio remains high. The results suggest that the intergalactic gas is more uniformly enriched in heavy elements than has been thought.

Antoinette Songaila Cowie
Last Revision : February, 1998