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arXiv · 1411.5375

Model-independent evidence in favor of an end to reionization by z~6

Ian McGreer·Andrei Mesinger·Valentina D'Odorico
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Abstract

We present new upper limits on the volume-weighted neutral hydrogen fraction, , at z~5-6 derived from spectroscopy of bright quasars. The fraction of the Lyman-alpha and Lyman-beta forests that is "dark" (with zero flux) provides the only model-independent upper limit on , requiring no assumptions about the physical conditions in the intergalactic medium or the quasar's unabsorbed UV continuum. In this work we update our previous results using a larger sample (22 objects) of medium-depth (~ few hours) spectra of high-redshift quasars obtained with the Magellan, MMT, and VLT. This significantly improves the upper bound on derived from dark pixel analysis to <= 0.06 + 0.05 (1σ) at z=5.9, and <= 0.04 + 0.05 (1σ) at z=5.6. These results provide robust constraints for theoretical models of reionization, and provide the strongest available evidence that reionization has completed (or is very nearly complete) by z~6.

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Ian McGreer, Andrei Mesinger, Valentina D'Odorico. 2014-11-19. Model-independent evidence in favor of an end to reionization by z~6. https://doi.org/10.1093/mnras%2Fstu2449

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