On the Size of HII Regions around High Redshift Quasars

Abstract

We investigate the possibility of constraining the ionization state of the intergalactic medium (IGM) close to the end of reionization (z ~ 6) by measuring the size of the HII regions in high-z quasars spectra. We perform a combination of multiphase smoothed particle hydrodynamics (SPH) and 3D radiative transfer (RT) simulations to reliably predict the properties of typical high-z quasar HII regions, embedded in a partly neutral IGM (x_HI=0.1). In this work we assume a fixed configuration for the quasar lifetime and luminosity, i.e. t_Q=10^7 yr and N_gamma=5.2 10^56 s-1. From the analysis of mock spectra along lines of sight through the simulated QSO environment, we find that the HII region size derived from quasar spectra is on average 30 per cent smaller than the physical one. Additional maximum likelihood analysis shows that this offset induces an overestimate of the neutral hydrogen fraction, x_HI, by a factor of 3. By applying the same statistical method to a sample of observed QSOs our study favors a mostly ionized (x_HI < 0.06) universe at z=6.1.

5 pages, 3 figures, accepted for publication in MNRAS Letters

References in corpus (3)

• Observational constraints on Cosmic Reionization
• The nature and evolution of the highly ionized near-zones in the absorption spectra of z~6 quasars
• Updating reionization scenarios after recent data

Cited by in corpus (21)

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• Luminosity Functions of Lyman Alpha Emitting Galaxies and Cosmic Reionization of Hydrogen
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• Lyman-alpha Emitters During the Early Stages of Reionization
• UV Radiative Feedback During the Advanced Stages of Reionization
• Lyman-alpha Damping Wing Constraints on Inhomogeneous Reionization
• Effect of the intergalactic environment on the observability of Ly-alpha emitters during reionization
• Mapping Neutral Hydrogen During Reionization with the Ly-alpha Emission from Quasar Ionization Fronts
• Searching for the reionization sources
• Signatures of reionization on Lyman alpha emitters
• Quasar H II Regions During Cosmic Reionization
• A closer look at using quasar near-zones as a probe of neutral hydrogen in the intergalactic medium
• Interpreting the Transmission Windows of Distant Quasars
• Simulating the impact of HI fluctuations on matched filter search for ionized bubbles in redshifted 21 cm maps
• Fossil Ionized Bubbles Around Dead Quasars During Reionization
• Can We Detect the Anisotropic Shapes of Quasar HII Regions During Reionization Through The Small-Scale Redshifted 21cm Power Spectrum?
• Constraining the epoch of reionization from the observed properties of the high-z Universe
• Optical-NIR spectra of quasars close to reionization (z~ 6)