Detection of candidate Lyα-emitting galaxies at z=5.7

We report the detection of seven candidate Ly alpha-emitting galaxies which have been found during the preliminary phase of the 'Calar Alto Deep Imaging Survey' (CADIS). They are selected from 147 emission-line galaxies detected in a field of 60 arcmin(2) with a Fabry-Perot interferometer, following the exclusion of 140 sources identified as foreground galaxies by a combination of broad-and narrow-band filters. Although no conclusive spectroscopic confirmation is yet available, we expect from an analysis of possible residual contamination by foreground objects that two or more of the candidates will turn out to be genuine Ly alpha-emitting primeval galaxies at a redshift of z=5.7. For a flat universe (q(0)=0.5) this would be in perfect agreement with refined predictions of the abundance of primeval galaxies and various recent results on the space density of young galaxies at z less than or equal to 4.5.