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Lyα emitters in a cosmological volume I : the impact of radiative transfer.

Gurung-López, Siddhartha and Orsi, Álvaro A. and Bonoli, Silvia and Baugh, Carlton M. and Lacey, Cedric G. (2019) 'Lyα emitters in a cosmological volume I : the impact of radiative transfer.', Monthly notices of the Royal Astronomical Society., 486 (2). pp. 1882-1906.


Lyman-α emitters (LAEs) are a promising target to probe the large scale structure of the Universe at high redshifts, z ≳ 2. However, their detection is sensitive to radiative transfer effects that depend on local astrophysical conditions. Thus, modeling the bulk properties of this galaxy population remains challenging for theoretical models. Here we develop a physically-motivated scheme to predict LAEs in cosmological simulations. The escape of Lyα photons is computed using a Monte Carlo radiative transfer code which outputs a Lyα escape fraction. To speed-up the process of assigning escape fractions to individual galaxies, we employ fitting formulae that approximate the full Monte Carlo results within an accuracy of 10% for a broad range of column densities, gas metallicities and gas bulk velocities. We apply our methodology to the semi-analytical model GALFORM on a large N-body simulation. The Lyα photons escape through an outflowing neutral gas medium, implemented assuming different geometries. This results in different predictions for the typical column density and outflow velocities of the LAE population. To understand the impact of radiative transfer on our predictions, we contrast our models against a simple abundance matching assignment. Our full models populate LAEs in less massive haloes than what is obtained with abundance matching. Overall, radiative transfer effects result in better agreement when confronting the properties of LAEs against observational measurements. This suggest that incorporating the effects of Lyα radiative transfer in the analysis of this galaxy population, including their clustering, can be important for obtaining an unbiased interpretation of future datasets.

Item Type:Article
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Publisher statement:© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:19 March 2019
Date deposited:04 April 2019
Date of first online publication:29 March 2019
Date first made open access:No date available

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