Stellar populations in early-type Coma cluster galaxies - I. The data

Abstract

We present a homogeneous and high signal-to-noise ratio data set (mean S/N ratio of ∼60 Å-1) of Lick/IDS stellar population line indices and central velocity dispersions for a sample of 132 bright (bj ≤ 18.0) galaxies within the central 1° (≡1.26 h-1 Mpc) of the nearby rich Coma cluster (A1656). Our observations include 73 per cent (100 out of 137) of the total early-type galaxy population (bj ≤ 18.0). Observations were made with the William Herschel 4.2-m telescope and the AUTOFIB2/WYFFOS multi-object spectroscopy instrument (resolution of ∼2.2-Å FWHM) using 2.7-arcsec diameter fibres (≡0.94 h-1 kpc). The data in this paper have well-characterized errors, calculated in a rigorous and statistical way. Data are compared with previous studies and are demonstrated to be of high quality and well calibrated on to the Lick/IDS system. Our data have median errors of ∼0.1 Å for atomic line indices, ∼0.008 mag for molecular line indices and 0.015 dex for velocity dispersions. This work provides a well-defined, high-quality baseline at z ~∼ 0 for studies of medium-to high-redshift clusters. Subsequent papers will use this data set to probe the stellar populations (which act as fossil records of galaxy formation and evolution) and the spectrophotometric relations of the bright early-type galaxies within the core of the Coma cluster.