INAF - Osservatorio Astronomico di Padova -

 Nearby Clusters: The WINGS survey

Figure 1:Isodensity contours with sub-structures in the cluster ZW-8852

 At low redshift, we lead the WIde-field Nearby Galaxy-cluster Survey (WINGS), a comprehensive survey of clusters and cluster galaxies in the local universe (0.04<z<0.07).
WINGS is an international collaboration, including astronomers from Italy (PD,TS), Spain, Denmark, USA and Australia, but it is coordinated and mostly carried out by Italian INAF astronomers in Padova.

The WINGS sample consists of a complete, X-ray flux-limited selection of 77 clusters in the redshift interval 0.04-0.07, with a wide range of X-ray and optical properties. WINGS entailed a huge observational effort, including optical imaging (B- and V-band) and spectroscopy, near-IR (J- and K-band) and U-band imaging, using wide-field cameras and spectrographs at 7 different telescopes in both hemispheres, for a total of ∼100 observing nights allocated so far. The WINGS database (imaging, spectroscopy and catalogues) is going to be released to the astronomical community, together with a friendly query interface. The main goal of this project is to carry out a systematic study of the cluster galaxy populations as a function of the global and local environment.

Figure 2:FP coefficients as a function of galaxy properties and local environment.

 The large field-of-view and the complementarity of the different sets of observations allows for the first time a detailed study of galaxy masses, morphologies and star formation histories from the densest regions in the cluster cores to the low-density outskirts of clusters and infalling groups and filaments. WINGS will provide a reliable zero point reference for studies of galaxies at higher redshifts, thus representing the local benchmark for evolutionary studies.
Up to now WINGS has produced:

• (i) integrated and aperture photometry in the optical (B,V; ∼400,000 galaxies), NIR (J,K; ∼700,000 galaxies) and U (∼150,000 galaxies) bands
;
• (ii) surface photometry (V-band) and morphology of ∼45,000 galaxies;
• (iii) redshift, line-widths and Lick-indices of ∼7,000 galaxies.

• (i) the automatic surface photometry of galaxies (GASPHOT);
• (ii) the automatic morphological type estimation (MORPHOT);
• (iii) the stellar population synthesis (including a reliable guess of the SFH).

Figure 3:Morphological fractions of WINGS clusters as a function of the cluster velocity dispersion and X-ray luminosity.

Scientific highlights so far concern the sub-structures, the Fundamental Plane (FP) of early-type galaxies and the morphological fractions.

1. From the 2D-analysis of sub-structures in the WINGS clusters (see Figure 1) we conclude that:
   (i) the fraction of clusters with subclusters (73%) is definitely higher than previously found;
   
   
   (ii) the distribution of subcluster luminosities (proportional to L
   ^-1
   ) is in agreement with the predictions of cosmological simulations;
   
   
   (iii) the magnitude difference between first- and second-ranked brightest cluster galaxies is significantly larger in clusters without sub-structures than in clusters with sub-structures.
2. By exploiting the surface photometry data from GASPHOT and the velocity dispersion data from SDSS and NFPS surveys, we analyse, for the WINGS early-type galaxies, the FP: Lg(R_e)=a*Lg(σ)+b*<μ_e>+c. We find that:
   (i) the FP coefficients suffer from a Malmquist-like bias, depending on the average photometric properties of the galaxy sample;
   
   
   (ii) the FP coefficients are strongly correlated with Sersic index and local environment (cluster centric distance and local density; see Figure 2) of galaxies, while they do not correlate with the global cluster properties.
3. In the WINGS clusters the spiral fraction turns out to be anticorrelated, and the S0 and elliptical fractions weakly correlated with the cluster X-ray luminosity, while no correlation is observed between morphological fractions and cluster velocity dispersion (see Figure 3). Since both velocity dispersion and X-ray luminosity are believed to be tracers of the cluster mass, these results pose a challenge for any current scenario of morphological evolution in clusters.
4. Analyses of the Color-Magnitude relation, of the Luminosity function of galaxies and of the 3D-structure of WINGS clusters are in progress.

People: D. Bettoni, G. Fasano, J. Fritz, B.M. Poggianti

Collaboration: M. D'Onofrio, T. Valentinuzzi (Padova Univ.), M. Ramella, A. Biviano (INAF OA Trieste), M. Moles, J. Iglesias, D. Reverte (IAA,ES), A. Aguerri, A. Cava, R. Janssen (IAC,ES), P. Kjaergaard (Copenhagen Univ., DK), W. Couch, D. Woods (NSW Univ. Sydney,AU), A. Dressler (Carnegie Inst. Pasadena,USA), A. Omizzolo (Vatican Observatory), E. Pignatelli, J. Varela .

Recent Publications Valentinuzzi et al. (2009), A&A in press; Varela et al. (2009), A&A in press; D'Onofrio et al. (2008), ApJ 685,875; Cava et al. (2008), arXiv 812.2022; Ramella et al. (2007) A&A 470,39; Fritz et al. (2007) A&A 470,137 Link: WINGS