G. Fasano

Superdense Massive Galaxies in Wings Local Clusters

Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M * > 4 × 1011 M ☉ compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

WINGS: a WIde-field Nearby Galaxy-cluster Survey. I. Optical imaging

This is the first paper of a series that will present data and scientific results from the WINGS project, a wide-field, multiwavelength imaging and spectroscopic survey of galaxies in 77 nearby clusters. The sample was extracted from the ROSAT catalogs of X-Ray emitting clusters, with constraints on the redshift (0.04 < z < 0.07) and distance from the galactic plane (|b |≥ 20 deg). The global goal of the WINGS project is the systematic study of the local cosmic variance of the cluster population and of the properties of cluster galaxies as a function of cluster properties and local environment. This data collection will allow the definition of a local, “zero-point” reference against which to gauge the cosmic evolution when compared to more distant clusters. The core of the project consists of wide-field optical imaging of the selected clusters in the B and V bands. We have also completed a multifiber, medium-resolution spectroscopic survey for 51 of the clusters in the master sample. The imaging and spectroscopy data were collected using, respectively, the WFC@INT and WYFFOS@WHT in the northern hemisphere, and the WFI@MPG and 2dF@AAT in the southern hemisphere. In addition, a NIR (J, K )s urvey of∼50 clusters and an Hα + U survey of some 10 clusters are presently ongoing with the WFCAM@UKIRT and WFC@INT, respectively, while a very-wide-field optical survey has also been programmed with OmegaCam@VST. In this paper we briefly outline the global objectives and the main characteristics of the WINGS project. Moreover, the observing strategy and the data reduction of the optical imaging survey (WINGS-OPT) are presented. We have achieved a photometric accuracy of ∼0.025 mag, reaching completeness toV ∼ 23.5. Field size and resolution (FWHM) span the absolute intervals (1.6–2.7) Mpc and (0.7–1.7) kpc, respectively, depending on the redshift and on the seeing. This allows the planned studies to obtain a valuable description of the local properties of clusters and galaxies in clusters.

The black hole mass of low redshift radiogalaxies

We make use of two empirical relations between the black hole mass and the global properties (bulge luminosity and stellar velocity dispersion) of nearby elliptical galaxies, to infer the mass of the central black hole (MBH) in low redshift radiogalaxies. Using the most recent determinations of black hole masses for inactive early type galaxies we show that the bulge luminosity and the central velocity dispersion are almost equally correlated (similar scatter) with the central black-hole mass. Applying these relations to two large and homogeneous datasets of radiogalaxies we find that they host black-holes whose mass ranges between � 5×10 7 to � 6×10 9 M⊙ (average �8.9). MBH is found to be proportional to the mass of the bulge (Mbulge). The distribution of the ratio MBH/Mbulge has a mean value of 8×10 −4 and shows a scatter that is consistent with that expected from the associated errors. At variance with previous claims no significant correlation is instead found between MBH (or Mbulge) and the radio power at 5 GHz.

Substructures in WINGS clusters

Aims. We search for and characterize substructures in the projected distribution of galaxies observed in the wide field CCD images of the 77 nearby clusters of the Wide-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in X-ray flux in the redshift range 0.04 < z < 0.07. Methods. We search for substructures in WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure on Monte-Carlo simulations of the observed frames and determine the reliability for the detected structures. Results. DEDICA identifies at least one reliable structure in the field of 55 clusters. 40 of these clusters have a total of 69 substructures at the same redshift of the cluster (redshift estimates of substructures are from color-magnitude diagrams). The fraction of clusters with subelusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ∼ 10 11 L ⊙ , our observed differential distribution of subeluster luminosities is consistent with the theoretical prediction of the differential mass function of substructures in cosmological simulations.

The manifold spectra and morphologies of EROs

Deep VLT optical spectroscopy, HST+ACS (GOODS) imaging and VLA observations are used to unveil the nature of a complete sample of 47 EROs with R−Ks > 5a ndKs < 20. The spectroscopic redshift completeness is 62%. Morphological classification was derived for each ERO through visual inspection and surface brightness profile fitting. Three main ERO morphological types are found: E/S0 galaxies (∼30−37%), spiral-like (∼24−46%) and irregular systems (∼17−39%). The only ERO detected in the radio is likely to host an obscured AGN. The average radio luminosity of the star-forming EROs undetected in the radio implies star formation rates of the order of ∼33 Myr −1 . The colors, redshifts and masses of the E/S0 galaxy subsample imply a minimum formation redshift zf ∼ 2. With this zf there is enough time to have old and massive stellar spheroids already assembled at z ∼ 1. We verify that the R − Ks vs. J − Ks color diagram is efficient in segregating old and dusty-star-forming EROs.

The fundamental plane of early-type galaxies in nearby clusters from the WINGS database

By exploting the data of three large surveys (WINGS, NFPS, and SDSS), we analyze the fundamental plane (FP) of early-type galaxies (ETGs) in 59 nearby clusters ( -->0.04 < z < 0.07). We show that the variances of the FP coefficients for our clusters are just marginally consistent with the hypothesis of universality of the FP. We found they are influenced by the distribution of photometric/kinematic properties of galaxies in the particular sample under analysis, suggesting that the FP is actually a bent surface. We also find a strong correlation between the local density and the FP coefficients, while they appear to be poorly correlated with the global properties of clusters. The relation between luminosity and mass of our galaxies, computed by assuming Sersic luminosity profiles, indicates that, for a given mass, the greater the light concentration, the higher the luminosity, while, for a given luminosity, the lower the light concentration, the greater the mass. Moreover, the M/L versus mass relation (again with Sersic profile fitting) turns out to be steeper and broader than that obtained for the Coma Cluster sample with de Vaucouleurs profile fitting. This broadness, together with the FP bending, might reconcile the FP phenomenology with the expectations from the ΛCDM cosmology. We conclude that the claimed universality of the FP of ETGs is still far from being proved and that systematic biases might affect the studies of luminosity evolution of ETGs, since data sets at different redshifts and with different distributions of the photometric/kinematic galaxy properties are compared each other.

The fundamental plane of radio galaxies

We collected photometrical and dynamical data for 73 low red-shift ( z< 0:2) Radio Galaxies (LzRG) in order to study their Fundamental Plane (FP). For 22 sources we also present new velocity dispersion data that complement the photometric data given in our previous study of LzRG (Govoni et al. 2000a). It is found that the FP of LzRG is similar to the one dened by non-active elliptical galaxies, with LzRG representing the brightest end of the population of early type galaxies. Since the FP mainly reflects the virial equilibrium condition, our result implies that the global properties of early{type galaxies (dening the FP) are not influenced by the presence of gas accretion in the central black hole. This is fully in agreement with the recent results in black hole demography, showing that virtually all luminous spheroidal galaxies host a massive black hole and therefore may potentially become active. We conrm and extend to giant ellipticals the systematic increase of the mass-to-light ratio with galaxy luminosity.

WINGS-SPE II: A catalog of stellar ages and star formation histories, stellar masses and dust extinction values for local clusters galaxies

Context. The WIde-field Nearby Galaxy clusters Survey (wings) is a project whose primary goal is to study the galaxy populations in clusters in the local universe (z < 0.07) and of the influence of environment on their stellar populations. This survey has provided the astronomical community with a high quality set of photometric and spectroscopic data for 77 and 48 nearby galaxy clusters, respectively. Aims. In this paper we present the catalog containing the properties of galaxies observed by the wings SPEctroscopic (WINGS-SPE) survey, which were derived using stellar populations synthesis modelling approach. We also check the consistency of our results with other data in the literature. Methods. Using a spectrophotometric model that reproduces the main features of observed spectra by summing the theoretical spectra of simple stellar populations of different ages, we derive the stellar masses, star formation histories, average age and dust attenuation of galaxies in our sample. Results. similar to 5300 spectra were analyzed with spectrophotometric techniques, and this allowed us to derive the star formation history, stellar masses and ages, and extinction for the wings spectroscopic sample that we present in this paper. Conclusions. The comparison with the total mass values of the same galaxies derived by other authors based on sdss data, confirms the reliability of the adopted methods and data.

A spectrophotometric model applied to cluster galaxies: the wings dataset

Context. The WIde-field Nearby Galaxy-cluster Survey (wings) is a project aiming at the study of the galaxy populations in clusters in the local universe (0.04 < z < 0.07) and the influence of environment on the physical properties of galaxies. This survey provides a high quality set of spectroscopic data for ∼6000 galaxies in 48 clusters. The study of such a large amount of objects requires automatic tools capable of extracting as much information as possible from the data. Aims. In this paper we describe a stellar population synthesis technique that reproduces the observed optical spectra of galaxies performing an analysis based on spectral fitting of the stellar content, extinction and, when possible, metallicity. Methods. A salient feature of this model is the possibility of treating dust extinction as a function of age, allowing younger stars to be more obscured than older ones. Our technique, for the first time, takes into account this feature in a spectral fitting code. A set of template spectra spanning a wide range of star formation histories is built, with features closely resembling those of typical spectra in our sample in terms of spectral resolution, noise and wavelength coverage. Our method of analyzing these spectra allows us to test the reliability and the uncertainties related to each physical parameter we are inferring. The well-known degeneracy problem, i.e. the non-uniqueness of the best fit solution (mass and extinction in different age bins), can be addressed by assigning adequate error bars to the recovered parameters. The values found in this way, together with their error bars, identify the region of parameter space which contains all the possible solutions for a given spectrum. A comparison test was also performed on a wings subsample, containing objects in common with the Sloan Digital Sky Survey, yielding excellent agreement. Results. We find that the stellar content as a function of age is reliably recovered in four main age bins and that the uncertainties only mildly depend on the S/N ratio. The metallicity of the dominant stellar population is not always recoverable unambiguosly, depending on the Star Formation History pattern.

GASPHOT: a tool for Galaxy Automatic Surface PHOTometry

In this paper we present a new tool for automatic, blind surface photometry of galaxies in deep and/or wide fields. The tool (GASPHOT) favors the robustness of results with respect to the details of galaxy modeling. To this aim, a single Sersic-law for the models and a hybrid 1D/2D approach for the best-fitting algorithm were adopted. GASPHOT is heavily based on SExtractor and provides luminosity, position angle and ellipticity profiles of galaxies extracted from CCD frames, as well as total magnitudes, half-light radii, and Sersic indices. These global parameters were obtained by simultaneously fitting the major and minor axis light growth curves of galaxies with a 2D flattened Sersic-law, convolved by the appropriate, space-varying PSF, which was previously evaluated by the tool itself. We tested GASPHOT on more than 15 000 simulated and real galaxies, obtaining robust upper limits for the errors of the global parameters of galaxies, even for non-Sersic profiles and blended objects. The GASPHOT performance was also compared with those of two popular alternative tools for a single component, Sersic law: GALFIT (Peng et al. 2002) and GIM2D (Marleau & Simard 1998). When dealing with ideal, isolated, and adeguately large galaxies, the three packages were all found to provide satisfactory results, apart from a definite bias in the GIM2D magnitudes. On the other hand, GASPHOT proved to be more robust than GALFIT and GIM2D for simulated, blended objects and for real galaxies. Moreover, at variance with GASPHOT and GALFIT, the quality (bias and scatter) of the fits provided by GIM2D rapidly declines as the galaxy size decreases.