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WINGS: a WIde-field Nearby Galaxy-cluster Survey. I. Optical imaging
This is the first paper of a series that will present data andscientific results from the WINGS project, a wide-field, multiwavelengthimaging and spectroscopic survey of galaxies in 77 nearby clusters. Thesample was extracted from the ROSAT catalogs of X-Ray emitting clusters,with constraints on the redshift (0.04< z<0.07) and distance fromthe galactic plane ({\vert}b{\vert}≥ 20 deg). The global goal of theWINGS project is the systematic study of the local cosmic variance ofthe cluster population and of the properties of cluster galaxies as afunction of cluster properties and local environment. This datacollection will allow the definition of a local, "zero-point" referenceagainst which to gauge the cosmic evolution when compared to moredistant clusters. The core of the project consists of wide-field opticalimaging of the selected clusters in the B and V bands. We have alsocompleted a multi-fiber, medium-resolution spectroscopic survey for 51of the clusters in the master sample. The imaging and spectroscopy datawere collected using, respectively, the WFC@INT and WYFFOS@WHT in thenorthern hemisphere, and the WFI@MPG and 2dF@AAT in the southernhemisphere. In addition, a NIR (J, K) survey of 50 clusters and anHα+U survey of some 10 clusters are presently ongoing with theWFCAM@UKIRT and WFC@INT, respectively, while a very-wide-field opticalsurvey has also been programmed with OmegaCam@VST. In this paper webriefly outline the global objectives and the main characteristics ofthe WINGS project. Moreover, the observing strategy and the datareduction of the optical imaging survey (WINGS-OPT) are presented. Wehave achieved a photometric accuracy of 0.025 mag, reachingcompleteness to V 23.5. Field size and resolution (FWHM) span theabsolute intervals (1.6-2.7) Mpc and (0.7-1.7) kpc, respectively,depending on the redshift and on the seeing. This allows the plannedstudies to obtain a valuable description of the local properties ofclusters and galaxies in clusters.
| Compact groups in dense environment: the case of IC 1370.
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| Power-spectrum normalization from the local abundance of rich clusters of galaxies
The number density of rich galaxy clusters still provides the mostrobust way of normalizing the power spectrum of dark matterperturbations on scales relevant to large-scale structure. We revisitthis constraint in the light of several recent developments: (1) theavailability of well-defined samples of local clusters with relativelyaccurate X-ray temperatures; (2) new theoretical mass functions for darkmatter haloes, which provide a good fit to large numerical simulations;(3) more accurate mass-temperature relations from larger catalogues ofhydrodynamical simulations; (4) the requirement to consider closed aswell as open and flat cosmologies to obtain full multiparameterlikelihood constraints for CMB and SNe studies. We present a new sampleof clusters drawn from the literature and use this sample to obtainimproved results on σ8, the normalization of the matterpower spectrum on scales of 8h-1Mpc, as a function of thematter density and cosmological constant in a universe with generalcurvature. We discuss our differences with previous work, and theremaining major sources of uncertainty. Final results on thenormalization, approximately independent of power spectrum shape, can beexpressed as constraints on σ at an appropriate clusternormalization scale RCl. We provide fitting formulas forRCl and σ(RCl) for general cosmologies, aswell as for σ8 as a function of cosmology and shapeparameter Γ. For flat models we find approximatelyσ8~=(0.495-0.037+0.034)ΩM-0.60 for Γ=0.23,where the error bar is dominated by uncertainty in the mass-temperaturerelation.
| A new local temperature distribution function for X-ray clusters: cosmological applications
We present a new determination of the local temperature function ofX-ray clusters using a sample of X-ray clusters with fluxes above 2.210-11erg/s/cm2 in the [0.1-2.4] keV band, most ofthese clusters come from the Abell XBAC's sample to which a handful ofknown non-Abell clusters has been added. We estimate this sample to be85% complete, and should therefore provide a useful estimation of thepresent-day number density of clusters. Comprising fifty clusters forwhich the temperature information is available, it is the largestcomplete sample of this kind. It is therefore expected to significantlyimprove the estimation of the temperature distribution function ofclusters. We find that the resulting temperature function is higher thanprevious estimations, but it agrees with the temperature distributionfunction inferred from the BCS and RASS luminosity function (Ebeling etal. 1997; De Grandi et al. 1999a). We have used this sample to constrainthe amplitude of the matter fluctuations sigma_c on cluster's scale of8sqrt [3]{Omega_0 }-1h-1Mpc, assuming amass-temperature relation based on recent numerical simulations. We findsigma_c ~ 0.6+/- 0.02 for an Omega_0 = 1 model (for which sigma_c =sigma_8 ). Our sample provides a useful reference at z ~ 0 to use in theapplication of the cosmological test based on the evolution of X-rayclusters abundance (Oukbir & Blanchard 1992, 1997). We havetherefore estimated the temperature distribution function at z = 0.33using Henry's sample of high-z X-ray clusters (Henry 1997; hereafterH97) and performed a preliminary estimate of Omega_0 . We find that theabundance of clusters at z = 0.33 is significantly smaller, by a factorlarger than 2, which shows that the EMSS sample provides strong evidencefor evolution of the cluster abundance. A likelihood analysis leads to arather high value of the mean density parameter of the universe: Omega_0= 0.92+0.255-0.215 (1 sigma ) for open universesand Omega_0 = 0.865+0.35-0.245 for flat universes,which is consistent with a previous independent estimation based on thefull EMSS sample by Sadat et al. (1998). Some systematic uncertaintieswhich could alter this result are briefly discussed.
| The ROSAT Brightest Cluster Sample - I. The compilation of the sample and the cluster log N-log S distribution
We present a 90 per cent flux-complete sample of the 201 X-ray-brightestclusters of galaxies in the northern hemisphere (delta>=0 deg), athigh Galactic latitudes (|b|>=20 deg), with measured redshiftsz<=0.3 and fluxes higher than 4.4x10^-12 erg cm^-2 s^-1 in the0.1-2.4 keV band. The sample, called the ROSAT Brightest Cluster Sample(BCS), is selected from ROSAT All-Sky Survey data and is the largestX-ray-selected cluster sample compiled to date. In addition to Abellclusters, which form the bulk of the sample, the BCS also contains theX-ray-brightest Zwicky clusters and other clusters selected from theirX-ray properties alone. Effort has been made to ensure the highestpossible completeness of the sample and the smallest possiblecontamination by non-cluster X-ray sources. X-ray fluxes are computedusing an algorithm tailored for the detection and characterization ofX-ray emission from galaxy clusters. These fluxes are accurate to betterthan 15 per cent (mean 1sigma error). We find the cumulative logN-logSdistribution of clusters to follow a power law kappa S^alpha withalpha=1.31^+0.06_-0.03 (errors are the 10th and 90th percentiles) downto fluxes of 2x10^-12 erg cm^-2 s^-1, i.e. considerably below the BCSflux limit. Although our best-fitting slope disagrees formally with thecanonical value of -1.5 for a Euclidean distribution, the BCS logN-logSdistribution is consistent with a non-evolving cluster population ifcosmological effects are taken into account. Our sample will allow us toexamine large-scale structure in the northern hemisphere, determine thespatial cluster-cluster correlation function, investigate correlationsbetween the X-ray and optical properties of the clusters, establish theX-ray luminosity function for galaxy clusters, and discuss theimplications of the results for cluster evolution.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Photoelectric Observations of Interacting and Compact Galaxies
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| Atmosphere of the Supergiant 6-CASSIOPEIAE - Part Three - Differential Shifts and Anomalies of the Line Profiles as a Manifestation of the Atmosphere Expansion and its Matter Loss
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| Catalogue no.10 of nebulae discovered at the Warner observatory.
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