Broadband Imaging Segregation of z ~ 3 Ly-alpha Emitting and Ly-alpha Absorbing Galaxies

TL;DR

This paper develops broadband photometric criteria to distinguish between Ly-alpha emitting and absorbing galaxies at z ~ 3, enabling large-scale, efficient selection for statistical studies, validated by spectroscopic follow-up.

Contribution

It introduces novel broadband selection criteria for Ly-alpha emitting and absorbing galaxies at z ~ 3, validated with spectroscopic data, facilitating large sample studies.

Findings

Criteria successfully select large samples of z ~ 3 LAEs and LBGs.

Spectroscopic confirmation supports the effectiveness of the selection.

Overlap between faint blue LBGs and LAEs suggests a continuum in galaxy properties.

Abstract

The spectral properties of Lyman break galaxies (LBGs) offer a means to isolate pure samples displaying either dominant Ly-alpha in absorption or Ly-alpha in emission using broadband information alone. We present criteria developed using a large z ~ 3 LBG spectroscopic sample from the literature that enables large numbers of each spectral type to be gathered in photometric data, providing good statistics for multiple applications. In addition, we find that the truncated faint, blue-end tail of z ~ 3 LBG population overlaps and leads directly into an expected Ly-alpha emitter (LAE) population. As a result, we present simple criteria to cleanly select large numbers of z ~ 3 LAEs in deep broadband surveys. We present the spectroscopic results of 32 r' <~ 25.5 LBGs and r' <~ 27.0 LAEs at z ~ 3 pre-selected in the Canada-France-Hawaii Telescope Legacy Survey that confirm these criteria.