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|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.
|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.
|Ionized gas in the nuclear regions of nearby non-Seyfert spiral galaxies|
A study of the distribution of ionized gas in the nuclear regions of astatistically significant sample of 91 non-Seyfert spirals is reported.CCD interference band images isolating the bright emission-lines ofH-alpha + forbidden N II (6548, 6583 A) have been used to map thedistribution of ionized gas in the inner 1-2 kpc of these galaxies. Thegalaxies exhibit a rich variety of nuclear and circumnuclearemission-line structures ranging from no-detectable emission to brightstellar nuclei with complicated circumnuclear emission regions extendingfor many kiloparsecs. Trends with Hubble-type and low-ionization nuclearemission-line spectral type (LINER or H II region) have been discerned.In galaxies with nuclear H II regions, those regions are on average thebrightest H II regions in their host galaxies. It appears thatnonthermal nuclear activity and nuclear star formation prefer differentnuclear environments, with active nuclei tending to be found inintermediate-type galaxies, and nuclear H II regions preferringlate-type spirals. It is speculated that this preference may be relatedto the dynamical properties of the host galaxies.
|Groups of galaxies in the Center for Astrophysics redshift survey|
By applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits.
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