| 1 | | Improving Constraints on Reionization with the Highest Known Redshift Quasar |
| | 1 | |
| | 2 | "The Unseen Sources of Early Enrichment and Reionization: |
| | 3 | Explanations for the Evolution of C IV Density at z = 5-6" |
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| | 5 | Abstract: |
| | 6 | In the near future, measurements of metal absorption features in the |
| | 7 | intergalactic medium (IGM) will become an important constraint on |
| | 8 | models of the formation and evolution of the earliest galaxies, the |
| | 9 | properties of the first stars, and the reionization and enrichment of |
| | 10 | the IGM. The first measurement of a metal abundance in the IGM at a |
| | 11 | redshift approaching the epoch of reionization already offers |
| | 12 | intriguing hints. Between z=5.8 and 4.7 (a 0.3 Gyr interval only 1 Gyr |
| | 13 | after the big bang), the measured density of CIV absorbers in the IGM |
| | 14 | increased by a factor of ~ 3.5 (Ryan-Weber et al. 2009; Becker, Rauch |
| | 15 | & Sargent 2009). If these values prove to be accurate, they pose two |
| | 16 | puzzles: (1) The total amount of CIV at z=5.8 implies too little star |
| | 17 | formation to reionize the IGM by z=6 or to match the WMAP electron |
| | 18 | scattering optical depth (tau). (2) The rapid growth from z = 6-5 is |
| | 19 | faster than the buildup of stellar mass or the increase in the star |
| | 20 | formation rate density over the same interval. We show that a delay of |
| | 21 | ~ 0.4-0.7 Gyr between the instantaneous production of ionizing photons |
| | 22 | and the later production of metal absorption features (added to the |
| | 23 | delay due to stellar lifetimes) can provide the full explanation for |
| | 24 | both puzzles. We calculate the delay in metal production due to finite |
| | 25 | stellar lifetimes alone and find that it is too short to explain the |
| | 26 | rapid CIV density increase. The additional delay could naturally be |
| | 27 | explained as the result of ~ 200 km/s outflows carrying carbon to |
| | 28 | distances of ~ 100 kpc, the typical distance between galaxies and CIV |
| | 29 | absorbers in enrichment simulations, and the typical outflow or |
| | 30 | absorption region scale observed at z ~ 2-3. |
