Mapping Lyman Continuum escape in Tololo 1247-232

TL;DR

This study uses HST imaging and ionization mapping to analyze the gas structure and star clusters in Tol 1247-232, revealing how ionization and starburst activity facilitate Lyman continuum escape in a low-redshift galaxy.

Contribution

It provides the first detailed spatially resolved analysis of LyC escape mechanisms in Tol 1247-232 using ionization mapping and stellar population modeling.

Findings

Global LyC escape fraction of 0.12 with uncertainties

Large-scale, optically thin regions from the galaxy center

Evidence of a two-stage starburst with recent clusters driving ionization

Abstract

Low redshift, spatially resolved Lyman continuum (LyC) emitters allow us to clarify the processes for LyC escape from these starburst galaxies. We use Hubble Space Telescope (HST) WFC3 and ACS imaging of the confirmed low-redshift LyC emitter Tol 1247-232 to study the ionization structure of the gas and its relation to the ionizing star clusters. We perform ionization parameter mapping (IPM) using [O III]4959, 5007 and [O II]3727 imaging as the high- and low-ionization tracers, revealing broad, large-scale, optically thin regions originating from the center, and reaching the outskirts of the galaxy, consistent with LyC escape. We carry out stellar population synthesis modeling of the 26 brightest clusters using our HST photometry. Combining these data with the nebular photometry, we find a global LyC escape fraction of f_esc = 0.12, with uncertainties also consistent with zero escape and with all measured f_esc values for this galaxy. Our analysis suggests that, similar to other candidate LyC emitters, a two-stage starburst has taken place in this galaxy, with a 12 Myr old, massive, central cluster likely having pre-cleared regions in and around the center, and the second generation of 2 - 4 Myr old clusters dominating the current ionization, including some escape from the galaxy.