Lyman alpha emitters with red colors at z~=2.4

TL;DR

This study identifies 58 Lyman alpha emitting galaxy candidates at z≈2.4 with red colors, suggesting they contain older stellar populations or are observed through special lines of sight, challenging simple star formation models.

Contribution

The paper presents a large-scale survey of red Lyman alpha emitters at z≈2.4, revealing their properties and implications for galaxy evolution and star formation history.

Findings

58 candidates detected with a density of ~0.07 per sq. arcmin

Most objects likely contain older stellar populations

Star formation rates inferred are extremely high, exceeding cosmic averages

Abstract

We have carried out a search for Lyman alpha emission from galaxies at z~=2.4 over a field of 1200 sq. arcmin using the CFH12K camera at the CFHT and a custom medium band filter. The search has uncovered 58 candidates, corresponding to a completeness-corrected source density of ~0.07 sq. arcmin^-2. Our sources have red colors (B-I~=1.8) which imply either that a large fraction of the light is highly reddened and we are detecting Lyman alpha through special lines of sight, or that these objects contain an underlying older stellar population. While for each individual object we cannot discriminate between these alternatives, we conclude that most of the objects actually contain an older component because the star formation rates inferred from the picture based on reddening, applied to all candidates, would imply an exceedingly high star formation rate, i.e. more than two orders of magnitude above the peak cosmic star formation rate (e.g. Lilly et al. 1996).