A Search for Primeval Galaxies Using a Narrow-Band Imaging Technique

A search has been made for faint emission-line objects by using a narrow-band imaging technique at wavelengths between 6000 and 8000 A. The observations are used to place constraints on the number density of Ly-alpha emission objects at redshifts of z = 4-6; either the surface density of primeval galaxies at z = 5 with strong Ly-alpha is less than about 0.1/sq arcmin, or such objects possess R magnitudes fainter than +27.5. Both of these possibilities appear to contravene current theoretical models, although a variety of explanations are possible.