Spectroscopy in Shapley supercluster

We describe the observations and measurements of central velocity dispersion {sigma}, emission-line equivalent widths and absorption-line indices. The distinguishing characteristic of the survey is its coverage of a very wide baseline in velocity dispersion (90 per cent range {sigma}=40-230km/s), while achieving high signal-to-noise ratio throughout (median 60{AA}^-1^ at 5000{AA}).

The data quality will enable estimates of Balmer-line ages to better than 20 per cent precision even for the faintest galaxies in the sample. Significant emission at H{alpha} was detected in ~30 per cent of the supercluster galaxies, including ~20 per cent of red-sequence members. Using line-ratio diagnostics, we find that the emission is LINER (low ionization nuclear emission region) like at high luminosity, but driven by star formation in low-luminosity galaxies.