WINGS: a WIde-field nearby Galaxy-cluster survey III. Deep near-infrared photometry of 28 nearby clusters

Context. This is the third paper of a series devoted to the WIde-field Nearby Galaxy-cluster Survey (WINGS).WINGS is a long term project aimed at gathering wide-field, multiband imaging and spectroscopy of galaxies in a complete sample of 77 X-ray selected nearby clusters (0.04<z<0.07) located far from the galactic plane (b>20deg). The main goal of this project is to establish a local reference sample for evolutionary studies of galaxies and galaxy clusters. Aims. This paper presents the near-infrared (J,K) photometric catalogs of 28 clusters of the WINGS sample and describes the procedures followed to construct them. Methods. The raw data has been reduced at CASU and special care has been devoted to the final coadding, drizzling technique, astrometric solution and magnitude calibration for the WFCAM pipeline processed data. We have constructed the photometric catalogs based on the final calibrated coadded mosaics (0.79 deg2) in J (19 clusters) and K (27 clusters) bands. A customized interactive pipeline has been used to clean the catalogs and to make mock images for photometric errors and completeness estimates. Results. We provide deep near-infrared photometric catalogs (90% complete in detection rate at total magnitudes J =20.5, K =19.4, and in classification rate at J = 19.5 and K = 18.5), giving positions, geometrical parameters, total and aperture magnitudes for all detected sources. For each field we classify the detected sources as stars, galaxies and objects of "unknown" nature.Comment: Published by A&A501.851 - 15 pages, 3 tables, 13 figures. Catalogs will be available via CDS and http://web.oapd.inaf.it/wing

Tunable Band Alignment with Unperturbed Carrier Mobility of On-Surface Synthesized Organic Semiconducting Wires

The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturisation of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursors, the product\u2019s energy level alignment can be tuned without compromising the charge carrier\u2019s mobility

The red-sequence of 72 WINGS local galaxy clusters

We study the color-magnitude red sequence and blue fraction of 72 X-ray selected galaxy clusters at z=0.04-0.07 from the WINGS survey, searching for correlations between the characteristics of the red sequence and the environment. We consider the slope and scatter of the red sequence, the number ratio of red luminous-to-faint galaxies, the blue fraction and the fractions of ellipticals, S0s and spirals that compose the red sequence. None of these quantities correlate with the cluster velocity dispersion, X-ray luminosity, number of cluster substructures, BCG prevalence over next brightest galaxies and spatial concentration of ellipticals. Instead, the properties of the red sequence depend strongly on local galaxy density. Higher density regions have a lower RS scatter, a higher luminous-to-faint ratio, a lower blue fraction, and a lower spiral fraction on the RS. Our results highlight the prominent effect of the local density in setting the epoch when galaxies become passive and join the red sequence, as opposed to the mass of the galaxy host structure.Comment: Accepted for publication in A&

The Shapes of BCGs and normal Ellipticals in Nearby Clusters

We compare the apparent axial ratio distributions of Brightest Cluster Galaxies (BCGs) and normal ellipticals (Es) in our sample of 75 galaxy clusters from the WINGS survey. Most BCGs in our clusters (69%) are classified as cD galaxies. The sample of cDs has been completed by 14 additional cDs (non-BCGs) we found in our clusters. We find that: (i) Es have triaxial shape, the triaxiality sharing almost evenly the intrinsic axial ratios parameter space, with a weak preference for prolateness; (ii) the BCGs have triaxial shape as well. However, their tendence towards prolateness is much stronger than in the case of Es. Such a strong prolateness appears entirely due to the sizeable (dominant) component of cDs inside the WINGS sample of BCGs. In fact, while the 'normal'(non-cD) BCGs do not differ from Es, as far as the shape distribution is concerned, the axial ratio distribution of BCG_cD galaxies is found to support quite prolate shapes; (iii) our result turns out to be strongly at variance with the only similar, previous analysis by Ryden et al.(1993)(RLP93), where BCGs and Es were found to share the same axial ratio distribution; (iv) our data suggest that the above discrepancy is mainly caused by the different criteria that RLP93 and ourselves use to select the cluster samples, coupled with a preference of cDs to reside in powerful X-ray emitting clusters; (v) the GIF2 N-body results suggest that the prolateness of the BCGs (in particular the cDs) could reflect the shape of the associated dark matter halos.Comment: 18 pages, 9 figures, 2 tables. Accepted for publication in MNRA

Frequency and properties of bars in cluster and field galaxies at intermediate redshifts

We present a study of large-scale bars in field and cluster environments out to redshifts of ~0.8 using a final sample of 945 moderately inclined disk galaxies drawn from the EDisCS project. We characterize bars and their host galaxies and look for relations between the presence of a bar and the properties of the underlying disk. We investigate whether the fraction and properties of bars in clusters are different from their counterparts in the field. The total optical bar fraction in the redshift range z=0.4-0.8 (median z=0.60), averaged over the entire sample, is 25% (20% for strong bars). For the cluster and field subsamples, we measure bar fractions of 24% and 29%, respectively. We find that bars in clusters are on average longer than in the field and preferentially found close to the cluster center, where the bar fraction is somewhat higher (~31%) than at larger distances (~18%). These findings however rely on a relatively small subsample and might be affected by small number statistics. In agreement with local studies, we find that disk-dominated galaxies have a higher optical bar fraction (~45%) than bulge-dominated galaxies (~15%). This result is based on Hubble types and effective radii and does not change with redshift. The latter finding implies that bar formation or dissolution is strongly connected to the emergence of the morphological structure of a disk and is typically accompanied by a transition in the Hubble type. (abridged)Comment: 17 pages, accepted for publication in A&

Substructures in WINGS clusters

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. 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. 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 subclusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ~ 10^11.2 L_Sun, our observed differential distribution of subcluster luminosities is consistent with the theoretical prediction of the differential mass function of substructures in cosmological simulations.Comment: A&A accepted - figure 6 is available from http://adlibitum.oats.inaf.it/ramella/WINGSfig

The evolution of the star formation activity in galaxies and its dependence on environment

We study how the proportion of star-forming galaxies evolves between z=0.8 and z=0 as a function of galaxy environment, using the [OII] line in emission as a signature of ongoing star formation. Our high-z dataset comprises 16 clusters, 10 groups and another 250 galaxies in poorer groups and the field at z=0.4-0.8 from the ESO Distant Cluster Survey, plus another 9 massive clusters at similar redshifts. As a local comparison, we use samples of galaxy systems selected from the Sloan Digital Sky Survey at 0.04< z < 0.08. At high-z most systems follow a broad anticorrelation between the fraction of star-forming galaxies and the system velocity dispersion. At face value, this suggests that at z=0.4-0.8 the mass of the system largely determines the proportion of galaxies with ongoing star formation. At these redshifts the strength of star formation (as measured by the [OII] equivalent width) in star-forming galaxies is also found to vary systematically with environment. Sloan clusters have much lower fractions of star-forming galaxies than clusters at z=0.4-0.8 and, in contrast with the distant clusters, show a plateau for velocity dispersions $\ge 550 km s^-1$, where the fraction of galaxies with [OII] emission does not vary systematically with velocity dispersion. We quantify the evolution of the proportion of star-forming galaxies as a function of the system velocity dispersion and find it is strongest in intermediate-mass systems (sigma ~ 500-600 km s^-1 at z=0). To understand the origin of the observed trends, we use the Press-Schechter formalism and the Millennium Simulation and show that galaxy star formation histories may be closely related to the growth history of clusters and groups. We propose a scheme that is able to account for the observed relations between the star-forming fraction and \sigma [abridged].Comment: 28 pages, 19 figures, ApJ in pres