The Impact of a Percolating IGM on Redshifted 21 cm Observations of Quasar HII Regions
Aug, 200711 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 386 (2008) 1683-1694
e-Print:
- 0708.3716 [astro-ph]
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Abstract: (arXiv)
We assess the impact of inhomogeneous reionization on detection of HII regions surrounding luminous high redshift quasars using planned low-frequency radio telescopes. Our approach is to implement a semi-numerical scheme to calculate the 3-dimensional structure of ionized regions surrounding a massive halo at high redshift, including the ionizing influence of a luminous quasar. As part of our analysis we briefly contrast our scheme with published semi-numerical models. We calculate mock 21 cm spectra along the line-of-sight towards high redshift quasars, and estimate the ability of the planned Mileura Widefield Array to detect the presence of HII regions. The signal-to-noise for detection will drop as the characteristic bubble size grows during reionization because the quasars influence becomes less prominent. However quasars will imprint a detectable signature on observed 21 cm spectra that is distinct from a region of typical IGM. At epochs where the mean neutral fraction is ~30% or greater we find that neutral gas in the IGM surrounding a single 4.5 proper Mpc quasar HII region will be detectable in 1000 hours, while a neutral fraction of 15% could be detected in 1000 hr. A highly significant detection will be possible in only 100 hours for a stack of 10 smaller 3 proper Mpc HII regions. The accurate measurement of neutral fraction will be limited by systematic fluctuations between different lines-of-sight for single HII regions, and by limited angular resolution where the measurement is averaged over many lines-of-sight.References(42)
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