Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Properties of nearby clusters of galaxies. III. A 76, A 157, A 407, A 505, A 671, A 779, A 1700, A 2028, A 2040, A 2052 A 2063, A 2065, A 2593, A 2657, A 2670
We present F band photometry, from digitized 48-inch Palomar plates, of2818 galaxies brighter than m_3+3 in 15 Abell clusters. For each galaxy,absolute coordinates, magnitude, size, ellipticity and orientation aregiven. For each cluster we provide finding charts and contour maps ofthe galaxy surface density. The absolute coordinates of the galaxies ofother 8 clusters presented in the first paper of this series are alsoincluded.
| The Lumpy Cluster Abell 1185
Abell 1185, a richness class 1 cluster of galaxies (cz = 9800 km s^-1^),has kinematic and x-ray substructure. We measure 39 new velocities inits field, bringing the known cluster population to 82 galaxies within1.4 h^-1^ Mpc of the cluster center. The sample has a depth of m_R_ ~15.8, and no substantial spatial bias. In addition to the optical datawe reanalyze a deep (11459 s) Einstein x-ray observation. Clumps in thevelocity distribution of A1185 are localized on the sky. The Dressler-Shectman test confirms the existence of subclumps with >99%confidence. X-ray emission from the cluster also appears complex;contributions from individual galaxies within A1185 are detectable. Thebrightest unresolved x-ray source coincides with an elliptical galaxywhich contains an active LINER nucleus. Throughout the paper we defineH_0_= 100 h km s^-1^ Mpc^- -1^, and unless otherwise indicated, weassume h = 1.
| Properties of nearby clusters of galaxies. I - A 195, A 465, A 1185, A 1213, A 1413, A 1775, A 2319 and A 2597
A study of the properties of nearby clusters of galaxies has beenundertaken. This paper describes the data, derived from automated scansof photographic plates. Different methods for the evaluation of clustercenter, ellipticity, and orientation are compared, and errors areestimated by Monte Carlo simulations. Results are presented of theanalysis of 1256 galaxies brighter than m3 + 3 in eight Abell clusters.It is found that different methods give consistent estimates ofellipticity and orientation, provided the radial dependence of thesequantities is taken into account. It is also found that centraldensities are consistent with isothermal fits if the center is selectedas the baricenter of the cluster. For each galaxy, rectangularcoordinates, magnitude, size, ellipticity, and orientation are given.Each cluster is provided with identification maps and contour maps ofgalaxy surface density.
| Associations between quasi-stellar objects and galaxies
A table is presented here listing all close pairs of QSOs and galaxiesthat were found in a computer-aided search of catalogs of QSOs andbright galaxies and an extensive search of the literature. There is alarge excess of pairs with separations of 2 arcmin lor less, or about 60kpc, over the numbers expected if the configurations were accidental.The angular separation for 392 pairs adds to the evidence for physicalassociation, and it is shown that selection effects are not important. Ageneral rule is stated that QSOs tend to lie in the vicinity of normalgalaxies much more often than is expected by chance whether or not thegalaxies and the QSOs have the same redshifts. It is emphasized thatthis rule cannot be explained in terms of gravitational microlensing,and it is concluded that some part of the redshift of all classes ofactive nuclei is not associated with the expansion of the universe.
| The structure of brightest cluster members. II - Mergers
Surface photometry of 342 bright elliptical galaxies in 103 clusters isanalyzed for evidence of mergers. Structural differences betweenbrightest cluster members (BCMs) and normal ellipticals can besummarized as having enlarged characteristic radii and shallow profileslopes (beta greater than -1.7). Profile morphology criteria for theelliptical types gE, D, and cD are outlined. Comparison of observationswith numerical simulations of mergers strongly suggests a past historyof dynamical growth for BCMs. Weak correlations of global clusterproperties to BCMs supports the hypothesis proposed by Merritt (1984)that mergers are important in early subgroups before virialization andformation of a cluster identity.
| A VLA 20 CM survey of poor groups of galaxies
The paper reports on VLA 20 cm observations of an extensive sample ofgalaxies in 139 poor groups. These groups, composed of galaxies down tothe limit of the Zwicky et al. (CGCG) catalog, were chosen using apercolation algorithm set at a high surface-density threshold.Approximately 50 percent of the groups have measured redshifts. Thesegroups were surveyed using a 'snapshot' mode of the VLA with aresolution of about 13 arcsec. Analysis of the resulting radio andoptical properties reveals that the presence of a nearby companiongalaxy has an important role in generating radio emission in a galaxy.CCD observations of two radio-loud, disturbed galaxies with companionsare presented and are used to discuss models of radio-source production.Nine tailed radio galaxies are found in the poor groups, which is muchmore than had been expected from previous work on rich clusters and fromtheoretical models. The paper discusses previous statistical biases andproposes a method for bending head-tail sources in poor groups. From theconfinement of extended radio features associated with tailed sources,the presence of a substantial intracluster medium that should radiatesignificantly at soft-X-ray energies is predicted.
| A catalog of morphological types in 55 rich clusters of galaxies
Data are presented from a study of 55 rich clusters of galaxies. Thedata include positions, morphological types, estimated total magnitudes,bulge sizes, and ellipticities for about 6000 galaxies, as determinedfrom high scale photographic plates. Data reduction procedures aredescribed, and a brief analysis of cluster richness, which indicatesthat Abell richness classes are only rough indicators of total clustermembership, is included.
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
Catálogos y designaciones:
|
