OmegaWINGS: spectroscopy in the outskirts of local clusters of galaxies

Abstract

Context. Studies of the properties of low-redshift cluster galaxies suffer, in general, from small spatial coverage of the cluster area. WINGS, the most homogeneous and complete study of galaxies in dense environments to date, obtained spectroscopic redshifts for 48 clusters at a median redshift of 0.05, out to an average distance of approximately 0.5 cluster virial radii. The WINGS photometric survey was recently extended by the VST survey OmegaWINGS to cover the outskirts of a subset of the original cluster sample. Aims. In this work, we present the spectroscopic follow-up of 33 of the 46 clusters of galaxies observed with VST over 1 square degree. The aim of this spectroscopic survey is to enlarge the number of cluster members and study the galaxy characteristics and the cluster dynamical properties out to large radii, reaching the virial radius and beyond. Methods. We used the AAOmega spectrograph at AAT to obtain fiber-integrated spectra covering the wavelength region between 3800 and 9000 Å with a spectral resolution of 3.5−6 Å full width at half maximum (FWHM). Observations were performed using two different configurations and exposure times per cluster. We measured redshifts using both absorption and emission lines and used them to derive the cluster redshifts and velocity dispersions. Results. We present here the redshift measurements for 17 985 galaxies, 7497 of which turned out to be cluster members. The sample magnitude completeness is 80% at V = 20. Thanks to the observing strategy, the radial completeness turned out to be relatively constant (90%) within the AAOmega field of view. The success rate in measuring redshifts is 95%, at all radii. Conclusions. We provide redshifts for the full sample of galaxies in OmegaWINGS clusters together with updated and robust cluster redshift and velocity dispersions. These data, publicly accessible through the CDS and VO archives, will enable evolutionary and environmental studies of cluster properties, providing a local benchmark.

GASP. I. Gas Stripping Phenomena in Galaxies with MUSE

“…The quality and characteristics of GASP data, which is very homogeneous for all targets, is best illustrated showing the results for one galaxy of the sample, JO206 6 (z=0.0513, WINGS J211347.41+022834.9), which was selected as a JClass=5 stripping candidate in the poor cluster IIZW108 (z=0.0486, Moretti et al 2017). JO206 is present in both the OMEGAWINGS (Gullieuszik et al 2015) and WINGS (Varela et al 2009) images, at RA=21 13 47.4 DEC= +02 28 35.5 (J2000).…”

Characterization of Omega-WINGS galaxy clusters

“…B-and V-band data for 46 WINGS clusters were obtained by Gullieuszik et al 2015 (see, e.g., Figure 1); these data cover an area of 1 • × 1 • . A spectroscopic follow up of 17985 galaxies in 34 clusters with the AAOmega spectrograph at AAT was also performed by Moretti et al 2017. Table A.1 in Appendix shows a recap of the observations carried out in the WINGS and Omega-WINGS surveys.…”

“…Finally, we removed all galaxies classified by Moretti et al (2017) as "non members" via a cross-check with the spectroscopic catalog. These objects were moved to a rejected sources catalog that was later used for improving the statistical field subtraction, as described in Section 3.3.…”

“…The first work is dedicated to the problem of the accurate determination of stellar light and stellar mass profiles of galaxy clusters. We exploit for this goal the large optical and spectroscopic database provided by the WIde-field Nearby Galaxy-cluster Survey (WINGS; Fasano et al 2006;Varela et al 2009;Cava et al 2009) and its Omega-WINGS extension (Gullieuszik et al 2015;Moretti et al 2017), which is available for nearby galaxy clusters (0.04 z 0.07). The first step carried out here provides the integrated luminosity (and stellar mass) profiles for 46 (42) nearby clusters.…”

Structural and dynamical modeling of WINGS clusters

“…Detailed information about spectral features are available for a subset of these galaxies (Fritz et al 2007(Fritz et al , 2011(Fritz et al , 2014. Follow-up spectroscopy of a subset of the WINGS clusters has been obtained using the Anglo Australian Telescope (AAT) AAOmega spectrograph (Moretti et al 2017), to extend the spectroscopic coverage of the WINGS clusters in their outer regions. Detailed morphological information is not yet available for the AAT/AAOmega additional sample, so this is not considered in the present study.…”