A CLUSTER OF NASCENT GALAXIES AT Z=2

On a 6 hr Wide Field Camera exposure with the Hubble Space Telescope of the rich cluster CL 0939+4713, we have identified an apparent cluster of approximately 30 faint, extended objects with magnitudes 22 < r < 25. The objects are typically 1'' in size with bright central regions only a few tenths of an arcsecond in size, and are distributed over a region approximately 40'' long and 20'' wide. A simple statistical analysis indicates that the clustering is probably real. The size and appearance of the individual objects, their blue colors, and their clustering, leads us to speculate that they are associated, and that they considerably more distant than the cluster CL 0939+4713 at z = 0.40, probably at a redshift z > 1. Among the strongest concentration of these objects is an unresolved, extremely blue object with the spectrum of a QSO at z = 2.055. We suggest that many of the small, faint objects could be physically associated with this QSO. If so, we may have observed a population of very distant, but in other respects ''typical,'' galactic or protogalactic objects, by detecting sites of strong star formation in what appears to be an early and possibly chaotic stage of galaxy development. Objects of similar size and brightness are spread around the field; their number density represents a significant fraction of the faint galaxy counts done with ground-based imaging. This suggests that the ability to resolve small structure with HST may have focused our attention on an important class of objects that might be the best examples to date of nascent galaxies, the ancestors of common galaxies like the Milky Way.