Lyman alpha Radiative Transfer in Cosmological Simulations using Adaptive Mesh Refinement

TL;DR

This paper introduces a new adaptive mesh refinement code for simulating Lyman alpha radiative transfer in three-dimensional cosmological environments, revealing how gas clumpiness affects observable galaxy properties.

Contribution

The paper presents a novel numerical code capable of detailed Lyman alpha radiative transfer modeling in complex, adaptive grid structures, enhancing understanding of high-redshift galaxy observations.

Findings

Surface brightness varies by an order of magnitude with viewing angle.

Total flux can differ by a factor of 3-6 depending on the line of sight.

Proper scattering treatment explains diversity in galaxy emission profiles.

Abstract

A numerical code for solving various Lyman alpha (Lya) radiative transfer (RT) problems is presented. The code is suitable for an arbitrary, three-dimensional distribution of Lya emissivity, gas temperature, density, and velocity field. Capable of handling Lya RT in an adaptively refined grid-based structure, it enables detailed investigation of the effects of clumpiness of the interstellar (or intergalactic) medium. The code is tested against various geometrically and physically idealized configurations for which analytical solutions exist, and subsequently applied to three "Lyman-break galaxies", extracted from high-resolution cosmological simulations at redshift z = 3.6. Proper treatment of the Lya scattering reveals a diversity of surface brightness (SB) and line profiles. Specifically, for a given galaxy the maximum observed SB can vary by an order of magnitude, and the total flux by a factor of 3 - 6, depending on the viewing angle. This may provide an explanation for differences in observed properties of high-redshift galaxies, and in particular a possible physical link between Lyman-break galaxies and regular Lya emitters.