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Future Constraints On The Reionization History From GRB Afterglows

Presentation #109.07 in the session “Large Scale Structure”.

Published onJun 18, 2021
Future Constraints On The Reionization History From GRB Afterglows

We forecast the reionization history constraints, inferred from Lyman-alpha damping wing absorption features, for a future sample of ~ 20 z > 6 gamma-ray burst (GRB) afterglows using a Fisher matrix analysis. We determine the expected constraints on the average neutral fraction after marginalizing over parameters describing the size of the ionized regions around each GRB and the column density of local damped Lyman-alpha systems associated with the GRB host galaxies. Assuming follow-up spectroscopy of the afterglows with a fiducial signal-to-noise ratio of 20 per R=3,000 resolution element at the continuum, we find that the neutral fraction may be determined to better than 10-15% (1-sigma) accuracy from this data across multiple independent redshift bins at z ~ 6–10, spanning much of the Epoch of Reionization, although the precision degrades somewhat near the end of reionization. A more futuristic survey with 80 GRB afterglows at z > 6 can improve the precision here by a factor of 2 and extend measurements out to z ~ 14.

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