Compact Lyman-alpha Emitting Candidates at z~2.4 in Deep Medium-band HST WFPC2 Images

TL;DR

This study identifies a widespread population of compact Lyman-alpha emitting objects at z~2.4 across multiple HST fields, indicating early universe sub-galactic structures that could contribute to galaxy formation.

Contribution

It provides evidence for the widespread presence of z~2.4 Lyman-alpha emitters in multiple fields, supporting their role in early galaxy assembly.

Findings

Detection of 18 candidates in three new fields

Significant variation in candidate numbers across fields

Implication of large-scale structure at z~2.4

Abstract

Medium-band imaging with HST/WFPC2 in the F410M filter has previously revealed a population of compact Lyman-alpha emission objects around the radio galaxy 53W002 at z~2.4. We report detections of similar objects at z~2.4 in random, high-latitude HST parallel observations of three additional fields, lending support to the idea that they constitute a widespread population at these redshifts. The three new fields contain 18 Lyman-alpha candidates, in contrast to the 17 detected in the deeper exposure of the single WFPC2 field around 53W002. We find substantial differences in the number of candidates from field to field, suggesting that significant large-scale structure is already present in the galaxy distribution at this cosmic epoch. The likely existence of z~2.4 sub-galactic clumps in several random fields shows that these objects may have been common in the early universe and strengthens the argument that such objects may be responsible for the formation of a fraction of the luminous present-day galaxies through hierarchical merging.