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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.
| Compact groups in the UZC galaxy sample
Applying an automatic neighbour search algorithm to the 3D UZC galaxycatalogue (Falco et al. \cite{Falco}) we have identified 291 compactgroups (CGs) with radial velocity between 1000 and 10 000 kms-1. The sample is analysed to investigate whether Tripletsdisplay kinematical and morphological characteristics similar to higherorder CGs (Multiplets). It is found that Triplets constitute lowvelocity dispersion structures, have a gas-rich galaxy population andare typically retrieved in sparse environments. Conversely Multipletsshow higher velocity dispersion, include few gas-rich members and aregenerally embedded structures. Evidence hence emerges indicating thatTriplets and Multiplets, though sharing a common scale, correspond todifferent galaxy systems. Triplets are typically field structures whilstMultiplets are mainly subclumps (either temporarily projected orcollapsing) within larger structures. Simulations show that selectioneffects can only partially account for differences, but significantcontamination of Triplets by field galaxy interlopers could eventuallyinduce the observed dependences on multiplicity. Tables 1 and 2 are onlyavailable in electronic at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/35
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| 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.
| Neutral hydrogen in small groups of galaxies
Neutral hydrogen in 36 pairs and small groups of galaxies was studiedusing the Arecibo radio telescope. Potential groups were selected fromthe Uppsala General Catalogue of Galaxies of Nilson (1973) by a simplealgorithm with the aims of determining or improving redshifts forgalaxies in possible groups and of mapping some of the larger galaxiesto determine their internal dynamics. The H I spectra are examined indetail and problems of confusion in these and previous observations areaddressed. A simple analysis of the groups' mean dynamical mass suggeststhat the mass determined from the galaxies' rotation is sufficient tobind them, but there may be important unmodeled selection orcontamination problems. A simple method for estimating errors of H Ivelocity measurements is also derived.
| The IC 698 group of galaxies
H I line observations are used to investigate the dynamical stability ofIC 698, a small group of spiral galaxies in the Coma/A1367 supercluster.Accurate radial velocities for all six members and direct mass estimatesfor five are reported. The group appears well isolated from othergalaxies and has a surprisingly small velocity dispersion of 46 km/s.The group has a negative total energy satisfying the condition forgravitational stability. With a crossing time of 0.17/H, the galaxies inthe system could make about 2.5 passages through the group in a Hubbletime. The virial mass-to-light ratio of the group is in excellentagreement with the M/L(B) ratio of high-luminosity spiral galaxies. Itis shown that the mass estimate described by Bahcall and Tremaine (1981)must be generalized before it can be applied to groups with members ofmass comparable to IC 698.
| The distribution of the spiral galaxies in the direction of the Coma/A 1367 supercluster
The three-dimensional distribution of spiral galaxies is analyzed for a1080 sq deg region surrounding the Coma cluster, A 1367 and Zw 74-23(NGC 5416 cluster). H I observations of spiral galaxies having angulardiameters less than 2 arcmin, with the exception of six NGC objects andone IC object, are used, detecting 87 galaxies with 67 redshiftsreported for the first time. A population of faint isolated galaxies asmuch as 30 deg from Coma or A 1367 is found having radial velocitiesnear 7000 km/s, and a group between Coma and A 1367 is found containingno galaxies with m(p) less than 15.0. South of A 1367 three groups arefound located 12 deg from the core with radial velocities near 7000 km/sand a projected diameter less than 2 Mpc. South of 20 deg declination atleast four clusters and isolated galaxies are found which could be partof the southern extension of the Coma-A 1367 supercluster. Assuming allthe detected isolated spirals belong to the Coma-A 1367 supercluster,the angular extent of the supercluster is almost a radian in the planeof the sky.
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