A sample of mJy radio sources at 1.4 GHz in the Lynx and Hercules fields - I. Radio imaging, multicolour photometry and spectroscopy

With the goal of identifying high-redshift radio galaxies with Fanaroff-Riley class I (FR I) classification, here are presented high-resolution, wide-field radio observations, near-infrared and optical imaging and multi-object spectroscopy of two fields of the Leiden-Berkeley Deep Survey. These fields, Hercules.1 and Lynx.2, contain a complete sample of 81 radio sources with S_{1.4 GHz} > 0.5 mJy within 0.6 deg². This sample will form the basis for a study of the population and cosmic evolution of high-redshift, low-power, FR I radio sources which will be presented in Paper II. Currently, the host galaxy identification fraction is 86 per cent with 11 sources remaining unidentified at a level of r'≥ 25.2 mag (Hercules; four sources) or r'≥ 24.4 mag (Lynx; seven sources) or K≳ 20 mag. Spectroscopic redshifts have been determined for 49 per cent of the sample and photometric redshift estimates are presented for the remainder of the sample.