A deep radio survey in the ISO-ELAIS fields: optical identification with the APM catalogue

The optical identification programme is presented for a complete sample of 867 radio sources that were observed with the Very Large Array (VLA) within 4.22 deg(2) to S-1.4 GHz greater than or equal to 0.135 mJy (5 sigma). The area covered by the VLA survey is part of the regions of the sky that have been surveyed in the mid and far Infrared over the wavelength range 6.7-175 mum with ISO as part of the European Large Area ISO Survey (ELAIS). Optical identifications are made using the Automatic Plate-measuring Machine (APM) optical catalogue in E (similar to R) and O (similar to B) bands with approximate limiting magnitudes of similar to 20.0 and 21.5 mag, respectively. For 220 out of the 867 radio sources, likely identifications are proposed with an a posteriori identification percentage of 25%. The sample of identification has a reliability of 96% and a completeness of 80%.