The peculiar motions of early-type galaxies in two distant regions - II. The spectroscopic data

We present the spectroscopic data for the galaxies studied in the EFAR proj ect, which is designed to measure the properties and peculiar motions of ea rly-type galaxies in two distant regions. We have obtained 1319 spectra of 714 early-type galaxies over 33 observing runs on 10 different telescopes. We describe the observations and data reductions used to measure redshifts, velocity dispersions and the Mgb and Mg-2 Lick linestrength indices. Detai led simulations and intercomparison of the large number of repeat observati ons lead to reliable error estimates far all quantities. The measurements f rom different observing runs are calibrated to a common zero-point or scale before being combined, yielding a total of 706 redshifts, 676 velocity dis persions, 676 Mgb linestrengths and 582 Mg-2 linestrengths. The median esti mated errors in the combined measurements are Delta cz = 20 km s(-1), Delta sigma/sigma = 9.1 per cent, Delta Mgb/Mgb = 7.2 per cent and Delta Mg-2 = 0.015 mag. Comparison of our measurements with published data sets shows no systematic errors in the redshifts or velocity dispersions, and only small zero-point corrections to bring our linestrengths on to the standard Lick system. We have assigned galaxies to physical clusters by examining the lin e-of-sight velocity distributions based on EFAR and ZCAT redshifts, togethe r with the projected distributions on the sky. We derive mean redshifts and velocity dispersions for these clusters, which will be used in estimating distances and peculiar velocities and to test for trends in the galaxy popu lation with cluster mass, The spectroscopic parameters presented here for 7 06 galaxies combine high-quality data, uniform reduction and measurement pr ocedures, and detailed error analysis. They form the largest single set of velocity dispersions and linestrengths for early-type galaxies published to date.