A Monte Carlo simulation of the intergalactic absorption and the detectability of the Lyman continuum from distant galaxies

TL;DR

This paper presents a Monte Carlo simulation modeling intergalactic absorption to estimate the escape fraction of Lyman continuum radiation from distant galaxies, aligning well with observational data.

Contribution

It introduces a new empirical distribution function for intergalactic absorbers that reproduces observed statistics of various Lyman systems simultaneously.

Findings

Lyman series transmissions match observed redshift evolution.

Lyman continuum transmission agrees with rare observational estimates.

Probability of a clear line of sight at z~4 is about 20%."

Abstract

We have made a Monte Carlo simulation of the intergalactic absorption in order to model the Lyman continuum absorption, which is required to estimate the escape fraction of the Lyman continuum from distant galaxies. To input into the simulation, we derive an empirical distribution function of the intergalactic absorbers which reproduces recent observational statistics of the Lyman $\alpha$ forest, Lyman limit systems (LLSs), and damped Lyman $\alpha$ systems (DLAs) simultaneously. In particular, we assume a common functional form of the number evolution along the redshift for all types of absorbers. The Lyman series transmissions in our simulation reproduce the observed redshift evolution of the transmissions excellently, and the Lyman continuum transmission also agrees with an observed estimation which is still quite rare in the literature. The probability distribution of the Lyman $\alpha$ opacity in our simulation is log-normal with a tail towards a large opacity. This tail is produced by DLAs. The probability distribution of the Lyman continuum opacity in our simulation also show a broad tail towards a large opacity. This tail is produced by LLSs. Because of the rarity of LLSs, we have a chance to have a clean line of sight in the Lyman continuum even for $z\sim4$ with a probability of about 20%. Our simulation expects a good correlation between the Lyman continuum opacity and the Lyman $\alpha$ opacity, which may be useful to estimate the former from the latter for an individual line of sight.