The stellar populations of early-type galaxies -- I. Observations, line-strengths and stellar population parameters

TL;DR

This paper compiles a detailed catalogue of early-type galaxies across multiple clusters, providing measurements of their stellar populations and outlining methods for analyzing their ages, metallicities, and element ratios to study environmental effects.

Contribution

It presents a comprehensive galaxy catalogue with stellar population parameters and describes the methodology for measuring and calibrating Lick indices for future environmental analysis.

Findings

Catalogue includes 416 galaxies with detailed properties.

Stellar population parameters estimated for 219 early-type galaxies.

Methodology for measuring and calibrating Lick indices outlined.

Abstract

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.