========================================================================== J/MNRAS/381/1035 Spectroscopy in Shapley supercluster (Smith+, 2007) The following files can be converted to FITS (extension .fit or fit.gz) tables.dat ========================================================================== Query from: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/MNRAS/381/1035 ==========================================================================
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Beginning of ReadMe : J/MNRAS/381/1035 Spectroscopy in Shapley supercluster (Smith+, 2007) ================================================================================ A deep AAOmega survey of low-luminosity galaxies in the Shapley supercluster: stellar population trends. Smith R.J., Lucey J.R., Hudson M.J. <Mon. Not. R. Astron. Soc., 381, 1035-1052 (2007)> =2007MNRAS.381.1035S ================================================================================ ADC_Keywords: Clusters, galaxy ; Galaxies, spectra ; Spectroscopy Keywords: galaxies: clusters: general - galaxies: elliptical and lenticular, cD - galaxies: evolution Abstract: We present new optical spectroscopy for 342 R<18 galaxies in the Shapley supercluster (and 198 supplementary galaxies), obtained from 8-h integrations with the AAOmega facility at the Anglo-Australian Telescope. 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 60AA^-1^ at 5000AA). 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 Halpha 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. To characterize the absorption lines, we use the classical Lick indices in the spectral range 4000-5200AA. We introduce a new method for applying resolution corrections to the line-strength indices. We define a subset of galaxies with very low emission contamination, based on the Halpha line, and fit the index relations for this subset. The final sample analysed in this paper comprises 232 NFPS-selected galaxies meeting both the emission and the redshift criteria, of which 198 have measured velocity dispersions (i.e. are not unresolved). Description: Spectroscopic observations were made with the AAOmega system on the 3.9-m AAT, on the nights of 2006 April 26 and 29. AAOmega consists of the 2dF fibre positioner, linked to an efficient and stable bench-mounted dual-beam spectrograph.