Journal Article

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

J. Stuart B. Wyithe

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 1, pages 469-480
Published in print June 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI:
Redshifted 21-cm observations of high-redshift quasar proximity zones

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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 thei-drop-out technique (i.e. quasars atz∼ 6). We argue that while quasars atz < 6.5 seem to reside in the post-overlap IGM, they will still provide valuable probes of the late stages of the overlap era because the light-travel time across a quasar proximity zone should be comparable to the duration of overlap. For redshifted 21-cm observations within a 32-MHz bandpass, we find that the subtraction of a spectrally smooth foreground will not remove spectral features due to the proximity zone. These features could be used to measure the neutral hydrogen content of the IGM during the late stages of reionization. The density of quasars atz∼ 6 is now well constrained. We use the measured quasar luminosity function to estimate the prospects for discovery of high-redshift quasars in fields that will be observed by the Murchison Widefield Array.

Keywords: galaxies: high-redshift; intergalactic medium; cosmology: theory; diffuse radiation; large-scale structure of Universe

Journal Article.  9180 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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