Luminous early-type field galaxies at z~0.4 - I. Observations and redshift catalogue of 581 galaxies

We have compiled a sample of ~9600 bright, i<=18.95, red, b_J-r>2, candidate galaxies in an area of 220deg². These are luminous, L>L*, field early-type galaxies with redshifts 0.3<~z<~0.6. We present a redshift catalogue of a subsample of 581 targets. The galaxies were selected according to their broad-band b_Jri colours from United Kingdom Schmidt Telescope plates, and have a surface density on the sky of only ~50deg^-2. Such luminous field galaxies are virtually absent from published redshift surveys and the catalogue provides a large sample of the most luminous normal galaxies, at cosmological distances. The statistical properties of the galaxy spectra, including absorption-line and emission-line measures, are presented and a composite spectrum constructed. The nature of the sample, combined with the relatively bright apparent magnitudes, makes the galaxies suitable targets for several key investigations in galaxy evolution and cosmology.