The new sample of Giant radio sources - I. Radio imaging, optical identification and spectroscopy of selected candidates

A new sample of very large angular size radio sources has been selected fro m the 1.4 GHz VLA surveys: FIRST and NVSS. This sample will be very useful for an observational constraint on the time evolution of double radio sourc es, especially their size, predicted by numerous analytical models of such evolution (cf. Introduction). In this paper we present radio and optical da ta for a large fraction of the sample sources. They are: high-frequency VLA maps with very weak radio cores detected, deep optical images showing the identified faint host galaxies not visible on the DSS images, and optical s pectra of the identified galaxies brighter than about R approximate to 18.5 mag taken with the McDonald Observatory 2.1 m telescope. For 15 galaxies ( of which 4 do not belong to the complete sample) the redshift has been dete rmined. In the result, 44 per cent of galaxies in the complete sample have redshift data (with one exception all redshifts are less than 0.33), of whi ch 70 per cent have a linear size exceeding 1 Mpc. The photometric redshift estimates for other 11 galaxies with 19 mag<R<21.7 mag (0.3<z<0.5) predict their sizes much over 1 Mpc.