3D Lya radiation transfer. II. Fitting the Lyman break galaxy MS 1512-cB58 and implications for Lya emission in high-z starbursts

TL;DR

This study uses a 3D radiation transfer model to accurately reproduce the Lyman-alpha profile of a high-redshift galaxy, revealing how dust and gas influence observed emission and suggesting most Lyman-break galaxies have intrinsically strong Lyman-alpha emission.

Contribution

First to incorporate comprehensive 3D radiation transfer modeling with observational constraints to interpret Lyman-alpha profiles in high-redshift galaxies.

Findings

Reproduced the Lya profile of MS 1512--cB58 considering dust and gas effects.

Found that dust and HI column density shape the observed Lya emission.

Suggested most LBGs have intrinsically strong Lya emission, with observed variations due to transfer effects.

Abstract

Using our 3D Lya radiation transfer code, we compute the radiation transfer of Lya and UV continuum photons including dust. Observational constraints on the neutral gas (column density, kinematics, etc.) are taken from other analysis of this object. RESULTS: The observed Lya profile of MS 1512--cB58 is reproduced for the first time taking radiation transfer and all observational constraints into account. The observed absorption profile is found to result naturally from the observed amount of dust and the relatively high HI column density. Radiation transfer effects and suppresion by dust transform a strong intrinsic Lya emission with EW(Lya)>~ 60 Ang into the observed faint superposed Lya emission peak. We propose that the vast majority of LBGs have intrinsically EW(Lya)~60-80 Ang or larger, and that the main physical parameter responsible for the observed variety of Lya strengths and profiles in LBGs is N_H and the accompanying variation of the dust content. Observed EW(Lya) distributions, Lya luminosity functions, and related quantities must therefore be corrected for radiation transfer and dust effects. The implications from our scenario on the duty-cycle of Lya emitters are also discussed.