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arXiv · 1708.08927

Determining the Nature of Late Gunn-Peterson Troughs with Galaxy Surveys

Frederick B. Davies·George D. Becker·Steven R. Furlanetto
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Abstract

Recent observations have discovered long (up to ~110 Mpc/h), opaque Gunn-Peterson troughs in the z ~ 5.5 Lyman-alpha forest, which are challenging to explain with conventional models of the post-reionization intergalactic medium. Here we demonstrate that observations of the galaxy populations in the vicinity of the deepest troughs can distinguish two competing models for these features: deep voids where the ionizing background is weak due to fluctuations in the mean free path of ionizing photons would show a deficit of galaxies, while residual temperature variations from extended, inhomogeneous reionization would show an overdensity of galaxies. We use large (~550 Mpc/h) semi-numerical simulations of these competing explanations to predict the galaxy populations in the largest of the known troughs at z ~ 5.7. We quantify the strong correlation of Lyman-alpha effective optical depth and galaxy surface density in both models and estimate the degree to which realistic surveys can measure such a correlation. While a spectroscopic galaxy survey is ideal, we also show that a relatively inexpensive narrowband survey of Lyman-alpha-emitting galaxies is ~90% likely to distinguish between the competing models.

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Frederick B. Davies, George D. Becker, Steven R. Furlanetto. 2017-08-29. Determining the Nature of Late Gunn-Peterson Troughs with Galaxy Surveys. https://doi.org/10.3847/1538-4357%2Faac2d6

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