Spectroscopy Observations
The main goal of the WINGS-SPE spectroscopic follow-up program is to supply a complete and uniform set of spectroscopic data such as redshift, line indices, and line widths useful to investigate the dynamics of the clusters and derive star formation histories, star formation rates, and other structural and physical properties of cluster galaxies. We present redshifts for galaxies in 48 clusters belonging to the WINGS sample. In addition, we present cluster velocity dispersion measurements derived from our redshift data. These clusters comprise an almost complete X-ray selected sample of galaxy clusters at z=0.04 − 0.07.
The target selection was based on the available WINGS optical B, V photometry (Varela et al. 2009) and the aim of the target selection strategy was to maximize the chances of observing galaxies at the cluster redshift without biasing the cluster sample.
The spectroscopic observations were obtained over the course of 6 observing runs (22 nights) at the 4.2 m William Herschel Telescope using the AF2/WYFFOS multifiber spectrograph and 3 observing runs (11 nights) at the 3.9 m Anglo Australian Telescope using the 2dF multifiber spectrograph.
AF2/WYFFOS is the multi-object, wide-field, fiber spectrograph working at the 4.2m William Herschel Telescope (WHT) on La Palma. AF2/WYFFOS can allocate up to 150 fibres, each of 1.6 arcsec diameter. We typically allocated 60-70 fibers to objects in a given configuration, and on average, 15-20 sky fibers. The spectra were centred at a wavelength of 5100Å and covered the range ~3800–7000Å. Hence they covered many interesting spectral features ranging from Ca H&K in the blue to NaD in the red. The galaxies were divided into different configurations, depending on their luminosities. In the figure below a sample spectra for the northern sample is presented. Spectra of bright (left) and faint (right) galaxies are shown for the cluster A1983. The object IDs and V-band magnitudes are given in each panel.
For the southern sample, we used the Two-degree Field (2dF) multifiber spectrograph on the AAT (runs 7-9). This instrument can observe up to 400 objects simultaneously over a two degree field of view. The fiber diameter is 2′′ . The galaxies were again divided into two different configurations in order to observe multiple sets of galaxies brighter and fainter than V = 19.5 in the fiber. For each cluster we were able in this way to observe ∼ 150 − 200 target galaxies. Here below some spectra of the southern emisphere.
