The Low-Redshift Lyman Continuum Survey I: New, Diverse Local Lyman-Continuum Emitters

TL;DR

This study identifies and characterizes a diverse sample of local galaxies emitting Lyman continuum photons, providing new insights into their properties and escape fractions to better understand cosmic reionization.

Contribution

It presents the first large, diverse sample of low-redshift Lyman continuum emitters, nearly tripling known local sources and offering new measurements of their escape fractions.

Findings

35 Lyman continuum emitters detected with high confidence

Escape fractions up to 50% observed in some galaxies

More than doubling the number of local LCEs with significant escape fractions

Abstract

The origins of Lyman continuum (LyC) photons responsible for the reionization of the universe are as of yet unknown and highly contested. Detecting LyC photons from the epoch of reionization is not possible due to absorption by the intergalactic medium, which has prompted the development of several indirect diagnostics to infer the rate at which galaxies contribute LyC photons to reionize the universe by studying lower-redshift analogs. We present the Low-redshift Lyman Continuum Survey (LzLCS) comprising measurements made with HST/COS for a z=0.2-0.4 sample of 66 galaxies. After careful processing of the FUV spectra, we obtain a total of 35 Lyman continuum emitters (LCEs) detected with 97.725% confidence, nearly tripling the number of known local LCEs. We estimate escape fractions from the detected LyC flux and upper limits on the undetected LyC flux, finding a range of LyC escape fractions up to 50%. Of the 35 LzLCS LCEs, 12 have LyC escape fractions greater than 5%, more than doubling the number of known local LCEs with cosmologically relevant LyC escape.