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In the near future, measurements of metal absorption features in theintergalactic medium (IGM) will become an important constraint on models of theformation and evolution of the earliest galaxies, the properties of the firststars, and the reionization and enrichment of the IGM. The first measurement ofa metal abundance in the IGM at a redshift approaching the epoch ofreionization already offers intriguing hints. Between z=5.8 and 4.7 (a 0.3 Gyrinterval only 1 Gyr after the big bang), the measured density of CIV absorbersin the IGM increased by a factor of ~ 3.5 (Ryan-Weber et al. 2009; Becker,Rauch & Sargent 2009). If these values prove to be accurate, they pose twopuzzles: (1) The total amount of CIV at z=5.8 implies too little star formationto reionize the IGM by z=6 or to match the WMAP electron scattering opticaldepth (tau). (2) The rapid growth from z = 6-5 is faster than the buildup ofstellar mass or the increase in the star formation rate density over the sameinterval. We show that a delay of ~ 0.4-0.7 Gyr between the instantaneousproduction of ionizing photons and the later production of metal absorptionfeatures (added to the delay due to stellar lifetimes) can provide the fullexplanation for both puzzles. We calculate the delay in metal production due tofinite stellar lifetimes alone and find that it is too short to explain therapid CIV density increase. The additional delay could naturally be explainedas the result of ~ 200 km/s outflows carrying carbon to distances of ~ 100 kpc,the typical distance between galaxies and CIV absorbers in enrichmentsimulations, and the typical outflow or absorption region scale observed at z ~2-3.

Delayed Enrichment by Unseen Galaxies: Explaining the Rapid Rise in IGM CIV Absorption from z = 6-5