  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.
