Probing the Epoch of Reionization with the Lyman Alpha Forest at z~4-5

TL;DR

This paper demonstrates that the Lyman-alpha forest flux power spectrum at redshifts 4-5 can distinguish between different reionization scenarios, offering insights into the epoch of reionization using existing quasar data.

Contribution

It shows that current SDSS quasar spectra can differentiate reionization completion at z=6 versus z=9 through flux power spectrum analysis.

Findings

Reionization scenarios at z=6 and z=9 can be distinguished at ~7 sigma.

The redshift range 4-5 provides optimal conditions for probing reionization.

Lyman-alpha forest data at z=4-5 retains memory of reionization history.

Abstract

The inhomogeneous cosmological reionization process leaves tangible imprints in the intergalactic medium down to z=4-5. The Lyman-alpha forest flux power spectrum provides a potentially powerful probe of the epoch of reionization. With the existing SDSS I/II quasar sample we show that two cosmological reionization scenarios, one completing reionization at z=6 and the other at z=9, can be distinguished at ~7 sigma level by utilizing Lyman alpha forest absorption spectra at z=4.5+-0.5, in the absence of other physical processes that may also affect the Lyman alpha flux power spectrum. The redshift range z=4-5 may provide the best window, because there is still enough transmitted flux and quasars to measure precise statistics of the flux fluctuations, and the IGM still retains a significant amount of memory of reionization.