Constraints on ionizing photon production from the large-scale Lyα forest

Abstract

Recent work has shown that the z ≃ 2.5 Lyα forest on large scales encodes information about the galaxy and quasar populations that keep the intergalactic medium photoionized. We present the first forecasts for constraining the populations with data from current and next-generation surveys. At a minimum, the forest should tell us whether galaxies or, conversely, quasars dominate the photon production. The number density and clustering strength of the ionizing sources might be estimated to sub-10% precision with a DESI-like survey if degeneracies (e.g., with the photon mean-free-path, small-scale clustering power normalization, and potentially other astrophysical effects) can be broken by prior information. We demonstrate that when inhomogeneous ionization is correctly handled, constraints on dark energy do not degrade. © 2014. The American Astronomical Society. All rights reserved..