Constraints to the evolution of Ly-α bright galaxies between z = 3 and z = 6

Galaxies at high redshift with a strong Ly-α emission line trace massive star formation in the absence of dust, and can therefore be regarded as a prime signature of the first major starburst in galaxies. We report results of the Ly-α search within the Calar Alto Deep Imaging Survey (CADIS). With the imaging Fabry-Perot interferometer, CADIS can detect emission lines in three waveband windows free of night-sky emission lines at 700 nm, 820 nm, and 920 nm. The typical flux detection limit for Ly-α emission redshifted into these windows, Flim > 3 × 10 −20 Wm −2 , corresponds to (unobscured) star formation rates of >10 M� /yr at z = 6. Candidate Ly-α-emitting galaxies are selected from the total emission line sample, which contains more than 97% of objects at z 5 than the assumption of a non-evolving population would predict. Therefore we conclude that the Ly-α bright phase of primeval star formation episodes reached its peak at redshifts 3 < z < 6.