A Statistical Comparison of Line Strength Variations in Coma and Cluster Galaxies at z0.3

Data

The data used in our analysis were taken from previously published work; the purpose of this section is therefore only to give information about the data relevant to the goals of this paper.

The distant cluster data were taken from the studies of Couch & Sharples (1987;hereafter CS), Couch et al. (1994), and Couch et al. (1997). The data of CS were taken at the 3.9 meter Anglo-Australian Telescope (AAT) with the FOCAP multi-fiber spectrograph and the IPCS detector in August and September, 1985, and have a spectral resolution of 4 Å  FWHM. The Couch et al. (1994) and Couch et al. (1997) data were also taken at the AAT using the multi-slit Low Dispersion Survey Spectrograph (LDSS-1) and have a spectral resolution of 9 Å  FWHM. In total, 249 galaxy spectra are available, providing 147 radial velocity members between the three clusters. Of these, 95 have Hubble type classifications based on high resolution imaging taken with the Wide Field and Planetary Camera (WFPC) by HST Couch et al. (1997).

The Coma cluster data have been published by Caldwell et al. (1993) and Caldwell & Rose (1997), and the reduced galaxy spectra were kindly provided by the authors for this work. They consist of spectra for 63 elliptical, 120 S0, 4 spiral, and 3 unclassified galaxies at a resolution of 4 Å  FWHM. All of the Coma spectra are cluster members.

The rest-frame wavelength coverage of nearly all the spectra is 3900 5300 Å, i.e. from the Ca II H & K lines through to the Mg triplet. All of the galaxy spectra have been smoothed to the 9 Å  resolution of the LDSS-1 data to avoid any systematic effects in measuring the spectral indices.

© Copyright Astronomical Society of Australia 1997