The stellar populations of early-type galaxies -- I. Observations,
  line-strengths and stellar population parameters
  The influence of environment on the formation and evolution of early-type
galaxies is, as yet, an unresolved issue. Constraints can be placed on models
of early-type galaxy formation and evolution by examining their stellar
populations as a function of environment. We present a catalogue of galaxies
well suited to such an investigation. The magnitude-limited (b_J<19.45) sample
was drawn from four clusters (Coma, A1139, A3558, and A930 at <z>=0.04) and
their surrounds. The catalogue contains luminosities, redshifts, velocity
dispersions and Lick line strengths for 416 galaxies, of which 245 are
classified as early-types. Luminosity-weighted ages, metallicities, and
alpha-element abundance ratios have been estimated for 219 of these
early-types. We also outline the steps necessary for measuring fully-calibrated
Lick indices and estimating the associated stellar population parameters using
up-to-date methods and stellar population models. In a subsequent paper we
perform a detailed study of the stellar populations of early-type galaxies in
clusters and investigate the effects of environment.
