2000A&A...362..509V

We present a large-area survey for Hα emission at redshifts from 2.1 to 2.4, using a combination of deep narrow-band and broad-band imaging in the near-infrared K-band. Our survey covers half the comoving volume of the widest available survey to date, but goes considerably deeper. We target volumes containing known damped Lya systems and radio galaxies as well as random fields. We detect (in addition to the two radio galaxies and one known active galaxy) four Hα emission objects, with implied star formation rates of 44 to 73h₇₅^–2M_☉/yr for q₀=0.1 and no extinction correction. It is argued that these objects are most likely star forming galaxies at z=2.1-2.4. The density of such sources in fields targeted at absorption line systems is found to be much higher than that in the vicinity of radio galaxies or quasars or in the general field at these redshifts. We discuss the properties of our detected sources and target fields, and suggest how future surveys of this type can be used to derive the cosmic star formation history.