Redshifted 21cm 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 21cm emission between a large HII region and the surrounding neutral inter-galactic 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 21cm 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 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 21cm observations within a 32MHz 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 at z~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.

14 pages, 9 figures. Accepted for publication in MNRAS

References in corpus (9)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• A Survey of z~6 Quasars in the SDSS Deep Stripe: I. a Flux-Limited Sample at z_{AB}<21
• The nature and evolution of the highly ionized near-zones in the absorption spectra of z~6 quasars
• Quasar Proximity Zones and Patchy Reionization
• The SDSS-DR5 Survey for Proximate Damped Lya Systems
• Detecting ionized bubbles in redshifted 21 cm maps
• A closer look at using quasar near-zones as a probe of neutral hydrogen in the intergalactic medium
• Are There Enough Ionizing Photons to Reionize the Universe by z=6?

Cited by in corpus (3)

• Simulating the impact of HI fluctuations on matched filter search for ionized bubbles in redshifted 21 cm maps
• Probing quasar lifetimes with proximate $21$-centimetre absorption in the diffuse intergalactic medium at redshifts $z\ge 6$
• Probing Cosmological Reionization through Radio-interferometric Observations of Neutral Hydrogen