Redshifted 21-cm observations of high-redshift quasar proximity zones

Abstract

The introduction of low-frequency radio arrays is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21-cm emission between a large H ii region and the surrounding neutral intergalactic medium (IGM) will be the simplest and most easily interpreted signature. However, the highest redshift quasars known are thought to reside in an ionized IGM. Using a semi-analytic model we describe the redshifted 21-cm signal from the IGM surrounding quasars discovered using the i-drop-out technique (i.e. quasars at z ∼ 6). We argue that while quasars at z < 6.5 seem to reside in the post-overlap IGM, they will still provide valuable probes of the late sta..