A closer look at using quasar near-zones as a probe of neutral hydrogen in the intergalactic medium

Abstract

We examine a large set of synthetic quasar spectra to realistically assess the potential of using the relative sizes of highly ionized near-zones in the Lya and Lyb forest as a probe of the neutral hydrogen content of the intergalactic medium (IGM) at z>6. The scatter in the relative near-zone size distribution, induced by underlying fluctuations in the baryonic density field and the filtering of ionizing radiation, is considerable even for fixed assumptions about the IGM neutral fraction. As a consequence, the current observational data cannot distinguish between an IGM which is significantly neutral or highly ionized just above z=6. Under standard assumptions for quasar ages and ionizing luminosities, a future sample of several tens of high resolution Lya and Lyb near-zone spectra should be capable of distinguishing between a volume weighted neutral hydrogen fraction in the IGM which is greater or less than 10 per cent.

6 pages, 3 figures, accepted for publication in MNRAS letters

References in corpus (5)

• Observational constraints on Cosmic Reionization
• The nature and evolution of the highly ionized near-zones in the absorption spectra of z~6 quasars
• The discovery of the first luminous z~6 quasar in the UKIDSS Large Area Survey
• On the Size of HII Regions around High Redshift Quasars
• Wide Field Surveys and Astronomical Discovery Space

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