WIde-field Nearby Galaxy-cluster Survey Research Articles

Seyfert-1 galaxies in WINGS and Omega-WINGS

Type-1 nuclear activity is rare in low-redshift clusters of galaxies. An analysis of the WIde field Nearby Galaxy Cluster Survey (WINGS) and of its extension Omega-WINGS revealed only three Seyfert 1 galaxies that are cluster members. We present a focused analysis of their emission line properties according to the interpretation scheme known as the Eigenvector 1/main sequence of quasars. Nuclear activity of the cluster members appears to be modest in the context of low-z type-1 AGN; however, one of the three Seyfert galaxies (WINGS J201158.35–570512.1) is a candidate super-Eddington source. Some general implications on non-thermal activity in clusters are suggested by the low prevalence of Seyfert 1s in the survey, and by the prevalence ratio between type-2 and type-1 AGN, apparently much higher in the cluster environment than in the field.

Morphology Driven Evolution of Barred Galaxies in OMEGAWINGS Clusters

We present a study of barred galaxies in the cluster environment, exploiting a sample of galaxies drawn from the extended WIde-field Nearby Galaxy-cluster Survey (OmegaWINGS) that covers up to the outer regions of 32 local X-ray selected clusters. Barred galaxies are identified through a semiautomatic analysis of ellipticity and position angle profiles. We find, in agreement with previous studies, a strong codependence of the bar fraction with the galaxy stellar mass and morphological type, being maximum for massive late-type galaxies. The fraction of barred galaxies decreases with increasing cluster mass and with decreasing clustercentric distance, a dependence that vanishes once we control for morphological type, which indicates that the likelihood of a galaxy hosting a bar in the cluster environment is determined by its morphological transformation. At large clustercentric distances, we detect a dependence on the distance to the nearest neighbor galaxy, suggesting that tidal forces with close companions are able to suppress the formation of bars or even destroy them. Barred galaxies in our sample are either early-type, star-forming galaxies located within the virial radii of the clusters or late-type quenched galaxies found beyond the virial radii of the clusters. We propose a scenario in which already quenched barred galaxies that fall into the clusters are centrally rejuvenated by the interplay of the perturbed gas by ram pressure and the bar, in galaxies that are undergoing a morphological transformation.

The parallelism between galaxy clusters and early-type galaxies

Context. This is the second work dedicated to the observed parallelism between galaxy clusters (GCs) and early-type galaxies (ETGs). The focus is on the distribution of these systems in the scaling relations (SRs) observed when effective radii, effective surface brightness, total luminosities, and velocity dispersions are mutually correlated. Aims. Using the data of the Illustris simulation we speculate on the origin of the observed SRs. Methods. We compare the observational SRs extracted from the database of the WIde-field Nearby Galaxy-cluster Survey with the relevant parameters coming from the Illustris simulations. Then we use the simulated data at different redshift to infer the evolution of the SRs. Results. The comparison demonstrate that GCs at z ∼ 0 follow the same log(L)−​log(σ) relation of ETGs and that both in the log(⟨I⟩e)−​log(Re) and log(Re)−​log(M*) planes the distribution of GCs is along the sequence defined by the brightest and massive early-type galaxies (BCGs). The Illustris simulation reproduces the tails of the massive galaxies visible both in the log(⟨I⟩e)−​log(Re) and log(Re)−​log(M*) planes, but fails to give the correct estimate of the effective radii of the dwarf galaxies that appear too large and those of GCs that are too small. The evolution of the SRs up to z = 4 permits to reveal the complex evolutionary paths of galaxies in the SRs and indicate that the line marking the zone of exclusion, visible in the log(⟨I⟩e)−​log(Re) and the log(Re)−​log(M*) planes, is the trend followed by virialized and passively evolving systems. Conclusions. We speculate that the observed SRs originate from the intersection of the virial theorem and a relation L = L0′σβ where the luminosities depend on the star formation history.

The second u-band extension of the WINGS cluster survey

Context. This is the second u-band extension of the WIde-field Nearby Galaxy-cluster Survey (WINGS) whereby 39 clusters were imaged with the ESO-VLT survey telescope. This follows the first part of the survey which was performed with several telescopes of the northern hemisphere in the U Cousin–Bessel filter band covering 17 clusters. Aims. The u-band data, in combination with those already collected by the WINGS survey, permit a detailed multi-wavelength investigation of the properties of the member galaxies from the cluster center out to the periphery. Methods. We used SExtractor to derive the main properties of the galaxies in the observed fields and measure the u − V colors on circular apertures of increasing radius. The photometric accuracy of the magnitudes was calibrated with the standard stars and was tested by means of comparisons with the u-band data of the Sloan Digital Sky Survey (SDSS). Results. We present the catalogs of the photometric analysis performed by SExtractor. We also provide a brief analysis of the u − V versus V color–magnitude diagram of our clusters, the plots of the color as a function of the cluster-centric distance (for cluster members only), the mass–color relation and the correlation of the current star formation rate (SFR) with the absolute V and u magnitudes for the galaxies in the observed fields.

Structural and dynamical modeling of WINGS clusters

The orbital shapes of galaxies of different classes are a probe of their formation and evolution. The Bayesian MAMPOSSt mass-orbit modeling algorithm is used to jointly fit the distribution of elliptical, spiral-irregular, and lenticular galaxies in projected phase space, on three pseudo-clusters (built by stacking the clusters after re-normalizing their positions and velocities) of 54 regular clusters from the Wide-field Nearby Galaxy-clusters Survey (WINGS), with at least 30 member velocities. Our pseudo-clusters (i.e., stacks) contain nearly 5000 galaxies with available velocities and morphological types. Thirty runs of MAMPOSSt with different priors are presented. The highest MAMPOSSt likelihoods are obtained for generalized Navarro-Frenk-White (NFW) models with steeper inner slope, free-index Einasto models, and double NFW models for the cluster and the brightest cluster galaxy. However, there is no strong Bayesian evidence for a steeper profile than the NFW model. The mass concentration matches the predictions from cosmological simulations. Ellipticals usually best trace the mass distribution while S0s are close. Spiral galaxies show increasingly elongated orbits at increasing radii, as do S0s on two stacks, and ellipticals on one stack. The inner orbits of all three types in the three stacks are consistent with isotropy. Spiral galaxies should transform rapidly into early-types given their much larger extent in clusters. Elongated outer orbits are expected for the spirals, a consequence of their recent radial infall into the cluster. The less elongated orbits we find for early-types could be related to the longer time spent by these galaxies in the cluster. We demonstrate that two-body relaxation is too slow to explain the inner isotropy of the early types, which suggests that inner isotropy is the consequence of violent relaxation during major cluster mergers or dynamical friction and tidal braking acting on subclusters. We propose that the inner isotropy of the short-lived spirals is a selection effect of spirals passing only once through pericenter before being transformed into early-type morphologies.

Maximum parsimony analysis of the effect of the environment on the evolution of galaxies

Context. Galaxy evolution and the effect of the environment are most often studied using scaling relations or regression analyses around a given property. However, these approaches do not take into account the complexity of the physics of the galaxies and their diversity. Aims. We here investigate the effect of the cluster environment on the evolution of galaxies through multivariate, unsupervised classification and phylogenetic analyses applied to two relatively large samples from the Wide-field Nearby Galaxy-cluster Survey (WINGS), one of cluster members and one of field galaxies (2624 and 1476 objects, respectively). Methods. These samples are the largest ones ever analysed with a phylogenetic approach in astrophysics. To be able to use the maximum parsimony (cladistics) method, we first performed a pre-clustering in 300 clusters with a hierarchical clustering technique, before applying it to these pre-clusters. All these computations used seven parameters: B − V, log(Re), nV, ⟨μ⟩e, Hβ, D4000, and log(M*). Results. We have obtained a tree for the combined samples and do not find different evolutionary paths for cluster and field galaxies. However, the cluster galaxies seem to have accelerated evolution in the sense that they are statistically more diversified from a primitive common ancestor. The separate analyses show a hint of a slightly more regular evolution of the variables for the cluster galaxies, which may indicate they are more homogeneous compared to field galaxies in the sense that the groups of the latter appear to have more specific properties. On the tree for the cluster galaxies, there is a separate branch that gathers rejuvenated or stripped-off groups of galaxies. This branch is clearly visible on the colour-magnitude diagram, going back from the red sequence towards the blue one. On this diagram, the distribution and the evolutionary paths of galaxies are strikingly different for the two samples. Globally, we do not find any dominant variable able to explain either the groups or the tree structures. Rather, co-evolution appears everywhere, and could depend itself on environment or mass. Conclusions. This study is another demonstration that unsupervised machine learning is able to go beyond simple scaling relations by taking into account several properties together. The phylogenetic approach is invaluable in tracing the evolutionary scenarios and projecting them onto any bivariate diagram without any a priori modelling. Our WINGS galaxies are all at low redshift, and we now need to go to higher redshfits to find more primitive galaxies and complete the map of the evolutionary paths of present day galaxies.

The strong correlation between post-starburst fraction and environment

We examine a magnitude limited (MB ≤ −18.7) sample of post-starburst (PSB) galaxies at 0.03 < |$z$| < 0.11 in the different environments from the spectroscopic data set of the Padova Millennium Galaxy Group Catalogue and compare their incidence and properties with those of passive (PAS) and emission line galaxies (EML). PSB galaxies have a quite precise lifetime (<1–1.5 Gyr), and they hold important clues for understanding galaxy evolution. While the properties (stellar mass, absolute magnitude, colour) of PSBs do not depend on environment, their frequency increases going from single galaxies to binary systems to groups, both considering the incidence with respect to the global number of galaxies and to the number of currently|$+$|recently star-forming galaxies. Including in our analysis, the sample of cluster PSBs drawn from the WIde-field Nearby Galaxy-cluster Survey presented in Paccagnella et al., we extend the halo mass range covered and present a coherent picture of the effect of the environment on galaxy transformations. We find that the PSB/(PSB |$+$| EML) fraction steadily increases with halo mass going from 1 per cent in |$10^{11} \, \mathrm{M}_{\odot}$| haloes to ∼15 per cent in the most massive haloes (⁠|$10^{15.5} \, \mathrm{M}_{\odot}$|⁠). This provides evidence that processes specific to the densest environments, such as ram-pressure stripping, are responsible for a large fraction of PSB galaxies in dense environments. These processes act on a larger fraction of galaxies than alternative processes leading to PSB galaxies in the sparsest environments, such as galaxy interactions.

Emission line galaxies and active galactic nuclei in WINGS clusters

We present the analysis of the emission line galaxies members of 46 low redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey, Fasano et al. 2006). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star forming galaxies and classified employing diagnostic diagrams. We have examined the emission line properties and frequencies of star forming galaxies, transition objects and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency with respect to control samples, and by a systematically lower Balmer emission line equivalent width and luminosity (up to one order of magnitude in equivalent width with respect to control samples for transition objects) that implies a lower amount of ionised gas per unit mass and a lower star formation rate if the source is classified as Hii region. A sizable population of transition objects and of low-luminosity LINERs (approx. 10 - 20% of all emission line galaxies) is detected among WINGS cluster galaxies. With respect to Hii sources they are a factor of approx. 1.5 more frequent than (or at least as frequent as) in control samples. Transition objects and LINERs in cluster are most affected in terms of line equivalent width by the environment and appear predominantly consistent with "retired" galaxies. Shock heating can be a possible gas excitation mechanism able to account for observed line ratios. Specific to the cluster environment, we suggest interaction between atomic and molecular gas and the intracluster medium as a possible physical cause of line-emitting shocks.

SLOW QUENCHING OF STAR FORMATION IN OMEGAWINGS CLUSTERS: GALAXIES IN TRANSITION IN THE LOCAL UNIVERSE

ABSTRACT The star formation quenching depends on environment, but a full understanding of what mechanisms drive it is still missing. Exploiting a sample of galaxies with masses M &ast; &gt; 10 9.8 M &CircleDot; ?> , drawn from the WIde-field Nearby Galaxy-cluster Survey (WINGS) and its recent extension OMEGAWINGS, we investigate the star formation rate (SFR) as a function of stellar mass (M &ast; ?> ) in galaxy clusters at 0.04 &lt; z &lt; 0.07 ?> . We use non-member galaxies at 0.02 &lt; z &lt; 0.09 as a field control sample. Overall, we find agreement between the SFR–M &ast; ?> relation in the two environments, but detect a population of cluster galaxies with reduced SFRs, which is rare in the field. These transition galaxies are mainly found within the cluster virial radius (R 200), but they impact on the SFR–M &ast; ?> relation only within 0.6R 200. The ratio of transition to pure star-forming galaxies strongly depends on environment, being larger than 0.6 within 0.3R 200 and rapidly decreasing with distance, while it is almost flat with M *. As galaxies move downward from the SFR–M &ast; ?> main sequence, they become redder and present older luminosity- and mass-weighted ages. These trends, together with the analysis of the star formation histories, suggest that transition galaxies have had a reduced SFR for the past 2–5 Gyr. Our results are consistent with the hypothesis that the interaction of galaxies with the intracluster medium via strangulation causes a gradual shut down of star formation, giving birth to an evolved population of galaxies in transition from being star forming to becoming passive.

OmegaWINGS: OmegaCAM-VST observations of WINGS galaxy clusters

The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z =0.04-0.07. The original 34'x34' WINGS field-of- view has now been extended to cover a 1 sq.deg field with both photometry and spectroscopy. In this paper we present the Johnson B and V-band OmegaCAM/VST observations of 46 WINGS clusters, together with the data reduction, data quality and Sextractor photometric catalogs. With a median seeing of 1arcs in both bands, our 25-minutes exposures in each band typically reach the 50% completeness level at V=23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS as well as with SDSS astrometry, and SDSS and previous WINGS imaging. Star/galaxy separation and sky-subtraction procedure have been tested comparing with previous WINGS data. The Sextractor photometric catalogues are publicly available at the CDS, and will be included in the next release of the WINGS database on the VO together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega/AAT and is being employed for a variety of studies. [abridged]

WINGS Data Release: a database of galaxies in nearby clusters

[Abridged] To effectively investigate galaxy formation and evolution, it is of paramount importance to exploit homogeneous data for large samples of galaxies in different environments. The WINGS (WIde-field Nearby Galaxy-cluster Survey) project aim is to evaluate physical properties of galaxies in a complete sample of low redshift clusters to be used as reference sample for evolutionary studies. The WINGS survey is still ongoing and the original dataset will soon be enlarged with new observations. This paper presents the entire collection of WINGS measurements obtained so far. We decided to make use of the Virtual Observatory (VO) tools to share the WINGS database (that will be regularly updated) with the community. In the database each object has one unique identification (WINGSID). Each subset of estimated properties is accessible using a simple cone search (including wide-field images). We provide the scientific community the entire set of wide-field images. Furthermore, the published database contains photometry of 759,024 objects and surface brightness analysis for 42,275 and 41,463 galaxies in the V and B band, respectively. The completeness depends on the image quality, and on the cluster redshift, reaching on average 90% at V<= 21.7. Near infrared photometric catalogs for 26 (in K) and 19 (in J) clusters are part of the database and the number of sources is 962,344 in K and 628,813 in J. Here again the completeness depends on the data quality, but it is on average higher than 90% for J<=20.5 and K<=19.4. The IR subsample with a Sersic fit comprises 71,687 objects. A morphological classification is available for 39,923 galaxies. We publish spectroscopic data, including 6,132 redshifts, 5,299 star formation histories and 4,381 equivalent widths. Finally, a calculation of local density is presented and implemented in the VO catalogs for 66,164 galaxies.

U-band photometry of 17 WINGS clusters

This paper belongs to a series presenting the WIde Field Nearby Galaxy-cluster Survey (WINGS). The WINGS project has collected wide-field, optical (B,V) and near-infrared (J,K) imaging, as well as medium resolution spectroscopy of galaxies in a sample of 76 X-ray selected nearby clusters (0.04 < z < 0.07), with the aim of establishing a reference sample for evolutionary studies of galaxies and galaxy clusters. In this paper we present the U-band photometry of galaxies and stars in the fields of 17 clusters of the WINGS sample. We also extend to a larger field of view the original B- and V-band photometry (WINGS-OPT) for 9 and 6 WINGS clusters, respectively. We use both the new and the already existing B-band photometry to get reliable (U-B) colors of galaxies within three fixed apertures in kpc. To this aim, in the reduction procedure we put particular care in the astrometric precision. Since not all the observations have been taken in good transparency conditions, the photometric calibration was partly obtained relying on the SDSS and WINGS-OPT photometry for the U- and optical bands, respectively. We provide U-band (also B- and V-band, where possible) total magnitudes of stars and galaxies in the fields of clusters. Just for galaxies, the catalogs also provide geometrical parameters and carefully centered aperture magnitudes. The internal consistency of magnitudes has been checked for clusters imaged with different cameras, while the external photometric consistency has been obtained comparing with the WINGS-OPT and SDSS surveys. The photometric catalogs presented here add the U-band information to the WINGS database for extending the SED of the galaxies, in particular in the UV wavelengths which are fundamental for deriving the SFR properties.

The impact of global environment on galaxy mass functions at low redshift

We study the galaxy stellar mass function in different environments in the local Universe, considering both the total mass function and that of individual galaxy morphological types. We compare the mass functions of galaxies with $\rm log_{10} M_{\star}/M_{\odot} \geq 10.25$ in the general field and in galaxy groups, binary and single galaxy systems from the Padova-Millennium Galaxy and Group Catalogue at $z=0.04-0.1$ with the mass function of galaxy clusters of the WIde-field Nearby Galaxy-Cluster Survey at $z=0.04-0.07$. Strikingly, the variations of the mass function with global environment, overall, are small and subtle. The shapes of the mass functions of the general field and clusters are indistinguishable, and only small, statistically insignificant variations are allowed in groups. Only the mass function of our single galaxies, representing the least massive haloes and comprising less than a third of the general field population, is proportionally richer in low-mass galaxies than other environments. The most notable environmental effect is a progressive change in the upper galaxy mass, with very massive galaxies found only in the most massive environments. This environment-dependent mass cut-off is unable to affect the Schechter parameters and the K-S test, and can only be revealed by an ad-hoc analysis. Finally, we show how, in each given environment, the mass function changes with morphological type, and that galaxies of the same morphological type can have different mass functions in different environments.

Active and star‐forming galactic nuclei in WINGS: A preliminary report

AbstractWe analyzed the spectra collected under the wide‐field nearby galaxy clusters survey (WINGS) to reveal emission lines in cluster galaxies. After removing stellar emission with dedicated population synthesis models we found evidence of faint emission line activity in a sizable number of sources. Diagnostic diagrams were used to define or at least constrain the origin of the emission line activity. Cross‐correlation with radio surveys is also being used for the identification of “true” active nuclei. We report the discovery of a previously unknown Seyfert 1 nucleus, WINGS J230945.81+072431.0, and preliminary results on prevalence and basic properties of the active and star forming galaxies we identified. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The importance of the local density in shaping the galaxy stellar mass functions★

Exploiting the capabilities of four different surveys --- the Padova-Millennium Galaxy and Group Catalogue (PM2GC), the WIde-field Nearby Galaxy-cluster Survey (WINGS), the IMACS Cluster Building Survey (ICBS) and the ESO Distant Cluster Survey (EDisCS) --- we analyze the galaxy stellar mass distribution as a function of local density in mass-limited samples, in the field and in clusters from low (z>0.04) to high (z<0.8) redshift. We find that at all redshifts and in all environments, local density plays a role in shaping the mass distribution. In the field, it regulates the shape of the mass function at any mass above the mass limits. In clusters, it seems to be important only at low masses (log M_ast/M_sun <10.1 in WINGS and log M_ast/M_sun < 10.4 in EDisCS), otherwise it seems not to influence the mass distribution. Putting together our results with those of Calvi et al. and Vulcani et al. for the global environment, we argue that at least at $z\leq 0.8$ local density is more important than global environment in determining the galaxy stellar mass distribution, suggesting that galaxy properties are not much dependent of halo mass, but do depend on local scale processes.

Galaxy stellar mass functions of different morphological types in clusters, and their evolution between z= 0.8 and 0

We present the galaxy stellar mass function and its evolution in clusters from z∼ 0.8 to the current epoch, based on the WIde-field Nearby Galaxy-cluster Survey (WINGS) (0.04 ≤z≤ 0.07), and the ESO Distant Cluster Survey (EDisCS) (0.4 ≤z≤ 0.8). We investigate the total mass function and find that it evolves noticeably with redshift. The shape at M* > 1011 M⊙ does not evolve, but below M*∼ 1010.8 M⊙ the mass function at high redshift is flat, while in the local Universe it flattens out at lower masses. The population of M*= 1010.2–1010.8 M⊙ galaxies must have grown significantly between z= 0.8 and 0. We analyse the mass functions of different morphological types (ellipticals, S0s and late types), and also find that each of them evolves with redshift. All types have proportionally more massive galaxies at high than at low-z, and the strongest evolution occurs among S0 galaxies. Examining the morphology–mass relation (the way the proportion of galaxies of different morphological types changes with galaxy mass), we find it strongly depends on redshift. At both redshifts, ∼40 per cent of the stellar mass is in elliptical galaxies. Another ∼43 per cent of the mass is in S0 galaxies in local clusters, while it is in late types in distant clusters. To explain the observed trends, we discuss the importance of those mechanisms that could shape the mass function. We conclude that mass growth due to star formation plays a crucial role in driving the evolution. It has to be accompanied by infall of galaxies on to clusters, and the mass distribution of infalling galaxies might be different from that of cluster galaxies. However, comparing with high-z field samples, we do not find conclusive evidence for such an environmental mass segregation. Our results suggest that star formation and infall change directly the mass function of late-type galaxies in clusters and, indirectly, that of early-type galaxies through subsequent morphological transformations.

The evolution of early-type galaxies in clusters from z∼ 0.8 to z ∼ 0: the ellipticity distribution and the morphological mix

We present the ellipticity distribution and its evolution for early-type galaxies in clusters from z~0.8 to z~0, based on the WIde-field Nearby Galaxy-cluster Survey (WINGS)(0.04<z<0.07), and the ESO Distant Cluster Survey (EDisCS)(0.4<z<0.8). We first investigate a mass limited sample and we find that, above a fixed mass limit, the ellipticity distribution of early-types noticeably evolves with redshift. In the local Universe there are proportionally more galaxies with higher ellipticity, hence flatter, than in distant clusters. This evolution is due partly to the change of the mass distribution and mainly to the change of the morphological mix with z (among the early types, the fraction of ellipticals goes from ~70% at high to ~40% at low-z). Analyzing separately the ellipticity distribution of the different morphological types, we find no evolution both for ellipticals and S0s. However, for ellipticals a change with redshift in the median value of the distributions is detected. This is due to a larger population of very round (e<0.05) elliptical galaxies at low-z. To compare our finding to previous studies, we also assemble a magnitude-"delimited" sample that consists of early-type galaxies on the red sequence with -19.3>M_B+1.208z>-21. Analyzing this sample, we do not recover exactly the same results of the mass-limited sample. Hence the selection criteria are crucial to characterize the galaxy properties: the choice of the magnitude-delimited sample implies the loss of many less massive galaxies and so it biases the final results. Moreover, although we are adopting the same selection criteria, our results in the magnitude-delimited sample are also not in agreement with those of Holden et al.(2009). This is due to the fact that our and their low-z samples have a different magnitude distribution because the Holden et al.(2009) sample suffers from incompleteness at faint magnitudes.

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

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. 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. 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. ~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. 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.

SUPERDENSE MASSIVE GALAXIES IN WINGS LOCAL CLUSTERS

Massive quiescent galaxies at z>1 have been found to have small physical sizes, 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<z<0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3x10^10Msol, are mostly S0 galaxies, have a median effective radius <Re> =1.61+/-0.29kpc, a median Sersic index <n> = 3.0+/-0.6, and very old stellar populations with a median mass-weighted age of 12.1+/-1.3Gyr. We calculate a number density of 2.9x10^-2Mpc^-3 for superdense galaxies in local clusters, and a hard lower limit of 1.3x10^-5Mpc^-3 in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that -when stellar masses are considered- there is consistency with the local WINGS galaxy sizes out to z~2, while a discrepancy of a factor of 3 exists with the only spectroscopic z>2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M*>4x10^11Msol compared to similarly massive galaxies in WINGS, i.e. the BCGs.

WINGS: a WIde-field nearby Galaxy-cluster survey

WINGS: a WIde-field nearby Galaxy-cluster survey