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O. V. Melnyk

Publications and source records attributed to O. V. Melnyk.

20 records · Page 2Linked to original sources

The Structure of the Local Supercluster of Galaxies Revealed by the Three-Dimensional Voronoi's Tessellation Method

3D Voronoi's tessellation method was first applied to identify groups of galaxies in the structure of a supercluster. The sample under consideration consists of more than 7000 galaxies of the Local Supercluster (LS) with radial velocities up to 3100 km/s. Because of an essential non-homogeneity of the LS catalogue, it was proposed to overscale distances in such an ''artificial'' way that the concentration of galaxies was varying as with increase of the distance a power-behaved function with the same exponent beta as for the full homogeneous catalogue. Various parameters of clustering were taking into account: alpha (0.01, 0.1, 1%) as the part of galaxies, which have the relative volume of a Voronoi's cell smaller than the critical one for the random distribution; beta = 0, which fits to the random galaxy distribution; beta = 0.7, which is close to the pancake galaxy distribution. It is revealed that Voronoi's tessellation method depends weakly on beta-parameter, and the number of galaxies in rich structures is growing rather than in poor ones with increase of alpha-parameter. The comparison of the groups derived with the groups obtained by Karachentsev's dynamical method shows that the number of groups, which coincides by all the components, is 22%. As a whole, the dynamical method is more preferred for identifying sparsely populated galaxy groups, whereas 3D Voronoi's tessellation method is preferred for more populated ones.

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Triplets of Galaxies in the Local Supercluster. I. Kinematic and Virial Parameters

We considered kinematic and virial parameters of a sample of galaxy triplets from the Local Supercluster (LS). The galaxies were selected from the LEDA database, and their radial velocities are no more than 3100 km/s. The sample contains 176 systems selected according to the Karachentsev criterion. We calculated the following median parameters of the LS triplets: rms velocity of galaxies with respect to triplet center, Sv=30 km/s; harmonic mean radius, Rh=160 kpc; virial mass Mvir=3.6x10^11 Msun; and mass-to-light ratio, Mvir/L=35 Msun/Lsun. Although various investigators used different approaches to compile samples of triple systems, general properties of the triplets in all the samples we considered agree rather satisfactorily. The LS triplets have the least mass-to-light ratio as compared to other galaxy triplet samples.

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