Limits on Lyman Continuum escape from z=2.2 H-alpha emitting galaxies

TL;DR

This study investigates the escape of Lyman continuum photons from z=2.2 H-alpha emitting galaxies, using Hubble UV imaging to set upper limits on the average escape fraction, informing galaxy contributions to cosmic reionization.

Contribution

The paper introduces a method to measure Lyman continuum escape fractions from H-alpha selected galaxies at z~2, demonstrating its application and potential for future large-scale studies.

Findings

No individual Lyman continuum detections in the sample.

Stacked data constrains the average escape fraction to less than 24%.

Method shows promise for robust future constraints with larger samples.

Abstract

The leakage of Lyman continuum photons from star forming galaxies is an elusive parameter. When observed, it provides a wealth of information on star formation in galaxies and the geometry of the interstellar medium, and puts constraints on the role of star forming galaxies in the reionization of the universe. H-alpha-selected galaxies at z~2 trace the highest star formation population at the peak of cosmic star formation history, providing a base for directly measuring Lyman continuum escape. Here we present this method, and highlight its benefits as well as caveats. We also use the method on 10 H-alpha emitters in the Chandra Deep Field South at z=2.2, also imaged with the Hubble Space Telescope in the ultraviolet. We find no individual Lyman continuum detections, and our stack puts a 5 sigma upper limit on the average absolute escape fraction of <24%, consistent with similar studies. With future planned observations, the sample sizes would rapidly increase and the method presented here would provide very robust constraints on the escape fraction.