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

Gurung-López, Siddhartha; Orsi, Álvaro A.; Bonoli, Silvia; Baugh, Carlton M.; Lacey, Cedric G.

Abstract

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.

Citation

Gurung-López, S., Orsi, Á. A., Bonoli, S., Baugh, C. M., & Lacey, C. G. (2019). Lyα emitters in a cosmological volume I: the impact of radiative transfer. Monthly Notices of the Royal Astronomical Society, 486(2), 1882-1906. https://doi.org/10.1093/mnras/stz838

• Journal Article Type: Article
• Acceptance Date: Mar 19, 2019
• Online Publication Date: Mar 29, 2019
• Publication Date: Jun 30, 2019
• Deposit Date: Apr 4, 2019
• Publicly Available Date: Apr 23, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 486
• Issue: 2
• Pages: 1882-1906
• DOI: https://doi.org/10.1093/mnras/stz838