Candidate primeval galaxies in the Hubble Deep Field.

Abstract

The authors present the results of colour selection of candidate high-redshift (2.6 < z < 3.9) galaxies within the Hubble Deep Field based on the Lyman break at 912 Å. The authors find eight such objects in the region, giving a comoving number density comparable to that of nearby bright galaxies (for a flat q₀ = 0.5, H₀ = 100 km s^-1Mpc^-1 universe). The authors provide basic data on the properties of these objects, and show that, despite their absolute magnitude being significantly brighter than L^* (typically M_B = -22), they are generally smaller than nearby galaxies. Furthermore, visual inspection of their images shows that they are all highly disturbed systems, with multiple nuclei, tails and plumes, suggesting that they are undergoing merging processes similar to those of most nearby starburst galaxies. Theoretical models suggest that galaxies form by accumulation of numerous subcomponents, and the authors suggest that we are seeing this process underway in these objects. It is thus possible that the epoch of galaxy formation might have been discovered.