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arXiv · 2109.13170

Constraints on the End of Reionization from the Density Fields Surrounding Two Highly Opaque Quasar Sightlines

Holly M. Christenson·George D. Becker·Steven R. Furlanetto·Frederick B. Davies·Matthew A. Malkan·Yongda Zhu·Elisa Boera·Adam Trapp
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Abstract

The observed large-scale scatter in Lyman $\alpha$ opacity of the intergalactic medium at $z<6$ implies large fluctuations in the neutral hydrogen fraction that are unexpected long after reionization has ended. A number of models have emerged to explain these fluctuations that make testable predictions for the relationship between Ly$\alpha$ opacity and density. We present selections of $z=5.7$ Ly$\alpha$-emitting galaxies (LAEs) in the fields surrounding two highly opaque quasar sightlines with long Ly$\alpha$ troughs. The fields lie towards the $z=6.0$ quasar ULAS J0148+0600, for which we re-analyze previously published results using improved photometric selection, and towards the $z=6.15$ quasar SDSS J1250+3130, for which results are presented here for the first time. In both fields, we report a deficit of LAEs within 20 $h^{-1}$ Mpc of the quasar. The association of highly opaque sightlines with galaxy underdensities in these two fields is consistent with models in which the scatter in Ly$\alpha$ opacity is driven by large-scale fluctuations in the ionizing UV background, or by an ultra-late reionization that has not yet concluded at $z=5.7$.

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Holly M. Christenson, George D. Becker, Steven R. Furlanetto, Frederick B. Davies, Matthew A. Malkan, Yongda Zhu, Elisa Boera, Adam Trapp. 2021-09-27. Constraints on the End of Reionization from the Density Fields Surrounding Two Highly Opaque Quasar Sightlines. https://doi.org/10.3847/1538-4357/ac2a34

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