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 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 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.

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 Two Species of Local Group Dwarf Spheroidals

1999 ◽  
Vol 192 ◽  
pp. 451-454
Author(s):  
Tsutomu T. Takeuchi ◽  
Hiroyuki Hirashita
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Star Formation Rate ◽  
Formation Rate ◽  
High Mass ◽  
Dwarf Spheroidal Galaxies ◽  
Total Luminosity ◽  
Virial Mass ◽  
Low Mass ◽  
Quantitative Explanation

We analyzed 10 dwarf spheroidal galaxies (dSphs) in the Local Group, and found two distinct sequences on the Mvir/L - Mvir plane: Mvir/L ∝ Mvir1.6 for Mvir < 108M⊙ whereas Mvir/L ≃ const. for Mvir > 108M⊙ (Mvir and L are the virial mass and the total luminosity of a dSph, respectively). We interpret the discontinuity as the threshold for the gas in dSphs to be blown away by successive supernovae. We succeeded in giving a quantitative explanation of the discontinuity mass of 108M⊙ as the blow-away condition. We further derived the above relation for the low-mass dSphs, assuming that the initial star formation rate of the dSphs is proportional to the inverse of the cooling time. The relation of high-mass dSphs is also explained along with the same consideration, with the condition that the gas cannot be blown away.

scholarly journals Photons in Curved Space?Time

1987 ◽  
Vol 40 (3) ◽  
pp. 449 ◽  
Author(s):  
David F Crawford
Keyword(s):  
Energy Loss ◽  
Loss Rate ◽  
Hubble Constant ◽  
Space Time ◽  
Quantum Mechanical ◽  
Clusters Of Galaxies ◽  
Hydrogen Atoms ◽  
Curved Space ◽  
Universal Expansion ◽  
Virial Mass

Because photons are described by quantum mechanical wavefunctions that have a nonzero spatial extent it follows that they can be influenced by curved space-time. It is generally assumed that this tidal interaction is far too small to have a significant effect. This paper argues that there is a significant effect that results in an interaction between the photon and the material causing the curved space-time in which the photon loses energy to low energy secondary photons. The energy loss is a function of the space-time curvature and is proportional to distance. The only situation fully considered is that of a photon in curved space-time due to a uniform distribution of matter. Because the energy loss rate is very small it is difficult to observe in the laboratory and therefore its major applications are in astronomy. If the intergalactic density of matter is n hydrogen atoms m - 3, then the predicted value for the 'Hubble' constant (assuming no universal expansion) is 51�68 n1 /2 km s - 1 Mpc - 1. The theory can solve the virial mass discrepancy observed in clusters of galaxies and it makes a definite prediction about their relative magnitudes. Other astronomical applications are considered.

RECOVERING THE INTERNAL DYNAMICS AND THE SHAPES OF GALAXY CLUSTERS: VIRGO CLUSTER

2002 ◽  
Vol 11 (04) ◽  
pp. 581-597
Author(s):  
V. G. GURZADYAN ◽  
S. RAUZY ◽  
R. TRIAY
Keyword(s):  
Galaxy Clusters ◽  
Virgo Cluster ◽  
Bulk Flow ◽  
Clusters Of Galaxies ◽  
Internal Dynamics ◽  
Dynamical Characteristics ◽  
Suggested Technique ◽  
Geometrical Shapes ◽  
Flow Velocities

We describe a method for recovering of the substructure, internal dynamics and geometrical shapes of clusters of galaxies. Applying the method to the Virgo cluster, we first, reveal the substructure of the central 4 arc degree field of the Virgo cluster by means of S-tree technique. The existence of three main subgroups of galaxies is revealed and their dynamical characteristics are estimated. Then, using the previously suggested technique (Ref. 1), the bulk flow velocities of the subgroups are evaluated based on the distribution of the redshifts of the galaxies. The results enable us also to obtain a secure indication of the elongation of the Virgo cluster and its positional inclination.

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 AGB stars and galactic dynamics

1999 ◽  
Vol 191 ◽  
pp. 500-510 ◽  
Author(s):  
H. Dejonghe ◽  
K. Van Caelenberg
Keyword(s):  
Chemical Composition ◽  
Stellar Population ◽  
Milky Way ◽  
Planetary Nebulae ◽  
Line Of Sight ◽  
Galactic Dynamics ◽  
Stellar Systems ◽  
Agb Stars ◽  
Dynamical Models ◽  
Ir Stars

AGB stars, seen as a stellar population, can be used to probe the dynamical state of galaxies. The relevant data are mostly positions and line-of-sight velocities, sometimes together with information on chemical composition and/or age. As of now, dynamical models have been made for OH/IR stars and Planetary Nebulae. Other candidates are C stars, S stars, and Miras. We review the methods used and the results obtained so far, for the Milky Way and for (relatively nearby) extragalactic stellar systems.

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