Sm. Pascarelle et al., Compact Ly alpha-emitting candidates at z similar or equal to 2.4 in deep medium-band Hubble Space Telescope WFPC2 images, ASTRONOM J, 116(6), 1998, pp. 2659-2666
Medium-band imaging with Hubble Space Telescope (HST) Wide Field Planetary
Camera 2 (WFPC2) in the F410M filter has previously revealed a population o
f compact Ly alpha emission objects around the radio galaxy 53W002 at z sim
ilar or equal to 2.4. We report detections of similar objects at z similar
or equal to 2.4 in random, high-latitude HST parallel observations of three
additional fields, lending support to the idea that they constitute a wide
spread population at these redshifts. The three new fields contain 18 Ly al
pha candidates, in contrast to the 17 detected in the deeper exposure of th
e single WFPC2 held around 53W002. We find substantial differences in the n
umber of candidates from held to field, suggesting that significant large-s
cale structure is already present in the galaxy distribution at this cosmic
epoch. The likely existence of z similar or equal to 2.4 subgalactic clump
s 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 r
esponsible for the formation of a fraction of the luminous present-day gala
xies through hierarchical merging.