scholarly journals Triple Galaxies and a Hidden Mass Problem

1990 ◽  
Vol 124 ◽  
pp. 115-127
Author(s):  
I.D. Karachentsev ◽  
V.E. Karachentseva ◽  
V.S. Lebedev
Keyword(s):  
Velocity Dispersion ◽  
Absolute Magnitude ◽  
Mass Excess ◽  
Homogeneous Sample ◽  
Groups Of Galaxies ◽  
Triple Systems ◽  
Crossing Time ◽  
Dynamical Parameters ◽  
Virial Mass ◽  
Harmonic Radius

AbstractWe consider a homogeneous sample of 84 triple systems of galaxies with components brighter than m = 15.7, located in the northern sky and satisfying an isolation criterion with respect to neighboring galaxies in projection. The distributions of basic dynamical parameters for triplets have median values as follows: radial velocity dispersion 133 km/s, mean harmonic radius 63 kpc, absolute magnitude of galaxies MB = —20.38, crossing time τ = 0.04 H−1. For different ways of estimation the median mass-to-luminosity ratio is (20 – 30)f⊙.A comparison of the last value with the ones for single and binary galaxies shows the presence of a virial mass excess for triplets by a factor 4. The mass-to-luminosity ratio is practically uncorrelated with linear size of triplets or with morphological types of their components.We note that a significant part of the virial excess may be explained by the presence of nonisolated triple configurations in the sample, which are produced by debris of more populous groups of galaxies.

Compact groups of galaxies (CGs) from the SDSS Data Release 6

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Xin-Fa Deng ◽  
Ji-Zhou He ◽  
Xin-sheng Ma ◽  
Peng Jiang ◽  
Xiao-Xun Tang
Keyword(s):  
Cluster Analysis ◽  
Velocity Dispersion ◽  
Three Dimensional ◽  
Compact Groups ◽  
Groups Of Galaxies ◽  
Main Galaxy ◽  
Crossing Time ◽  
Data Release ◽  
Galaxy Sample ◽  
Virial Mass

AbstractFrom the volume-limited MAIN galaxy sample of the SDSS Data Release 6 (SDSS6), we have identified 1298 compact groups of galaxies (CGs) at the neighbourhood radius of R = 1.2 Mpc by three-dimensional cluster analysis. In order to compile the CG catalog, we also estimated velocity dispersion, virial radius, virial mass and crossing time of CGs. In addition, our results show that properties of galaxies may not correlate with merging frequencies.

scholarly journals A new catalogue of multiple galaxies in the Local Supercluster

2000 ◽  
Vol 174 ◽  
pp. 40-45
Author(s):  
D. I. Makarov ◽  
I. D. Karachentsev
Keyword(s):  
New Approach ◽  
Galaxy Groups ◽  
Closed Orbits ◽  
Crossing Time ◽  
Local Supercluster ◽  
Virial Mass ◽  
Nearby Galaxies ◽  
The Individual ◽  
Group Member ◽  
Harmonic Radius

AbstractA new approach is suggested which makes use of the individual properties of galaxies, for the identification of small galaxy groups in the Local Supercluster. The criterion is based on the assumption of closed orbits of the companions around the dominating group member within a zero velocity sphere.The criterion is applied to a sample of 6321 nearby galaxies with radial velocities V0 ≤ 3000 km s−1. These 3472 galaxies have been assigned to 839 groups that include 55% of the sample considered. For the groups identified by the new algorithm (with k ≥ 5 members) the median velocity dispersion is 86 km s−1, the median harmonic radius is 247 kpc, the median crossing time is 0.08(1/H), and the median virial-mass-to-light ratio is 56 M⊙/L⊙.

scholarly journals The X-Ray Emitting Galaxy Group SHKH 360

1996 ◽  
Vol 171 ◽  
pp. 453-453
Author(s):  
H. Tiersch ◽  
H. Oleak ◽  
D. Stoll ◽  
A.D. Schwope ◽  
S. Neizvestny ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Red Shift ◽  
Space Density ◽  
X Ray ◽  
Strongly Interacting ◽  
Crossing Time ◽  
Virial Mass ◽  
Image Position

Shkh 360 has the characteristic signature of a strongly interacting group. Seven galaxies are embedded in a common extended halo and the isophotes indicate clear signs of alignment in B,V, and R. The parameters of the group as the red shift, z, the distance, d, the projected diameter, D, (basing on H = 55 km/s/Mpc), the virial radius, Rvir, the velocity dispersion, σv, the virial mass, the crossing time, τ, and the space density of galaxies, n, are given in the Table.

scholarly journals Dark Matter in Groups and Clusters of Galaxies

1995 ◽  
Vol 164 ◽  
pp. 454-454
Author(s):  
M. Kalinkov ◽  
I. Kuneva ◽  
I. Valtchanov
Keyword(s):  
Line Of Sight ◽  
Clusters Of Galaxies ◽  
Dynamical Models ◽  
Dynamical Characteristics ◽  
Velocity Statistics ◽  
Total Luminosity ◽  
Crossing Time ◽  
Pair Separation ◽  
Virial Mass ◽  
Harmonic Radius

Samples of groups, clusters and superclusters of galaxies have been collected from existing catalogs. The group sample consisted of 70 systems, the list of clusters contains 50 systems, and there are five superclusters. Kinematical and dynamical characteristics are obtained — elongation (along the line of sight, RA and Dec), velocity statistics, total luminosity, harmonic radius, mean pair separation, crossing time, virial mass … We have compared some of the observational features with dynamical models of groups, clusters and superclusters. Aarseth's (1985) code is used.

scholarly journals Southern triplets of galaxies

2000 ◽  
Vol 174 ◽  
pp. 11-24
Author(s):  
V. E. Karachentseva ◽  
I. D. Karachentsev
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Angular Separation ◽  
Absolute Magnitude ◽  
Radial Velocities ◽  
Dynamic Parameters ◽  
Sky Surveys ◽  
Triple Systems ◽  
Angular Diameters

AbstractUsing the ESO/SERC and POSS-I sky surveys we selected 76 isolated triple systems of galaxies with Dec. < −3°. For each triplet the equatorial coordinates, type of configuration, angular diameters, apparent angular separation of the components, morphological types, total magnitudes and some other characteristics are presented. 33 of 76 triplets have the measured radial velocities for all the components. The median values of basic dynamic parameters: a radial velocity dispersion, mean harmonic separation, an absolute magnitude of galaxies, mass-toluminosity ratio are very close to those obtained earlier for 83 northern isolated triple systems from the list of Karachentseva et al. (1979).

scholarly journals Observational Properties of Triple Galaxies

2000 ◽  
Vol 174 ◽  
pp. 1-10
Author(s):  
I. D. Karachentsev
Keyword(s):  
Narrow Range ◽  
Triple Systems ◽  
Galaxy Groups ◽  
Crossing Time ◽  
Local Supercluster ◽  
Virial Mass ◽  
Nearby Galaxies

AbstractThis report presents basic observational parameters for galaxy triplets selected by criterion of their isolation on the sky (=Catalog of Triple Galaxies, Karachentseva et al, 1979). The CTG sample is compared with a sample of wide triple systems from Nearby Galaxies Catalog (Tully, 1988) as well from a new whole-sky catalog of small galaxy groups in the Local Supercluster (Makarov & Karachentsev, 2000). For all the samples their medians of the virial mass-to-luminosity ratio lie in a narrow range, 31 < Mvir/L < 36 (M⊙/L⊙), while the medians of the crossing time occupy a wider range, 0.07 < Tcross < 0.37 (in 1/H units).

scholarly journals Poor Groups Around Strong Gravitational Lenses

2006 ◽  
Vol 2 (S235) ◽  
pp. 230-230
Author(s):  
Ivelina Momcheva ◽  
Kurtis Williams ◽  
Ann Zabludoff ◽  
Charles Keeton
Keyword(s):  
Galaxy Evolution ◽  
Velocity Dispersion ◽  
Gravitational Lenses ◽  
Local Universe ◽  
Groups Of Galaxies ◽  
Hot Gas ◽  
Gas Kinematics ◽  
The Galaxy ◽  
Group Centroid ◽  
Group Galaxy

AbstractPoor groups are common and interactive environments for galaxies, and thus are important laboratories for studying galaxy evolution. Unfortunately, little is known about groups at z ≥ 0.1, because of the difficulty in identifying them in the first place. Here we present results from our ongoing survey of the environments of strong gravitational lenses, in which we have so far discovered six distant (z ≥ 0.5) groups of galaxies. As in the local Universe, the highest velocity dispersion groups contain a brightest member spatially coincident with the group centroid, whereas lower-dispersion groups tend to have an offset brightest group galaxy. This suggests that higher-dispersion groups are more dynamically relaxed than lower-dispersion groups and that at least some evolved groups exist by z ~ 0.5. We also compare the galaxy and hot gas kinematics with those of similarly distant clusters and of nearby groups.

scholarly journals Simulations of Compact Groups of Galaxies with Halos

1987 ◽  
Vol 117 ◽  
pp. 281-281
Author(s):  
T. Ishizawa
Keyword(s):  
Velocity Dispersion ◽  
Big Bang ◽  
Compact Groups ◽  
Maximum Expansion ◽  
Groups Of Galaxies ◽  
Elapsed Time ◽  
Self Consistent ◽  
The Big Bang ◽  
Hubble Time

Self-consistent simulations of seven groups are performed from the maximum expansion to the present using Aarseth's N-body code. An initial galaxy consists of 100 stars. Its mass, half-mass radius, and central velocity dispersion are 1, 0.41, and 0.96. Units of mass, length, velocity, and time are 1.4×101 2M⊙, 100 kpc, 245 kms−1 and 4.0×108y. Table 1 gives the elapsed time from the Big Bang to the formation of a multiple merger tm+Tc*/2. For H0=80 kms−1Mpc−1, the Hubble time H0−1=30.6 in our units. Dense groups except B form multiple mergers in a Hubble time.

A Study of Three Groups of Galaxies: Plausible Explanation of the Virial Mass Discrepancy

1973 ◽  
Vol 186 ◽  
pp. 777 ◽  
Author(s):  
J. Richard, III Gott ◽  
Gerard T. Wrixon ◽  
Peter Wannier
Keyword(s):  
Groups Of Galaxies ◽  
Virial Mass

scholarly journals Compact Groups of Galaxies

1999 ◽  
Vol 186 ◽  
pp. 367-373
Author(s):  
P. Hickson
Keyword(s):  
Galaxy Evolution ◽  
Mass Velocity ◽  
Velocity Dispersion ◽  
Continuous Process ◽  
Physical Nature ◽  
Compact Groups ◽  
Early Type ◽  
Natural Explanation ◽  
Groups Of Galaxies ◽  
Formation And Evolution

This paper reviews some of the outstanding questions concerning compact groups of galaxies. These relate to the physical nature and dynamical status of the groups, their formation and evolution, and their role in galaxy evolution. The picture that emerges is that compact groups are generally physically dense systems, although often contaminated by optical projections. Their evolution is likely a continuous process of infall, interaction and merging. As new galaxies are added, and previous ones merge, the membership of the group evolves. I suggest that while the size of the group changes little, other physical properties such as total mass, gas mass, velocity dispersion, fraction of early-type galaxies increase with time. This picture is at least qualitatively consistent with observations and provides a natural explanation for the strongest correlations found in compact group samples.

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