On the ellipticity of the Shakhbazian compact groups of galaxies

Oleak, H.; Stoll, D.; Tiersch, H.; MacGillivray, H. T.

doi:10.1086/117378

Cited by 31 publications

(27 citation statements)

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“…It has been found that ShCGs have forms of prolate spheroids or "cigars" (Oleak et al 1995(Oleak et al , 1998. The distribution of the LG galaxies along the "cigar" shows that the whole CG+LG system has the same shape.…”

Section: Discussionmentioning

confidence: 99%

Shakhbazian compact groups: Poor clusters of galaxies

Tovmassian

Tiersch²

2001

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Abstract. The environment of 105 elongated (b/a < 0.5) ShCGs is investigated for galaxies probably associated with them. Counts of galaxies are made in two reciprocally orthogonal stripes of 5 width and 20 length passing through the center of each elongated group. The orientation of the first stripe is determined by the orientation of elongation of the distribution of the principal members of groups. It is found that there is an excess of galaxies in the narrow stripes oriented along the elongation of the group. Such peculiar distribution of the loose group members allows us to conclude that they are gravitationally bound with the compact group, and rotate around the common gravitational center. It is shown that the new-found distant members compose, together with the principal members of the compact group, a gravitationally bound, and, most probably, virialized system. All members of the system rotate around the common gravitational center. It is concluded that ShCGs are the cores of poor clusters of galaxies. They must be not young, and are relatively stable configurations. The number of such groups could be very high in the Universe.

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Section: Discussionmentioning

confidence: 99%

Shakhbazian compact groups: Poor clusters of galaxies

Tovmassian

Tiersch²

2001

A&A

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“…The knowledge of the correct positions of member galaxies of ShCGs allowed Oleak et al (1995Oleak et al ( , 1998 to investigate the apparent ellipticity of about 300 ShCGs using the method proposed by Rood (1979). It was found that the mean apparent axial ratio 2 b/a ∼ 0.5.…”

Section: Introductionmentioning

confidence: 99%

Shakhbazian compact galaxy groups

Tiersch¹,

Tovmassian²,

Stoll³

et al. 2002

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Abstract. Shakhbazian compact galaxy groups belong to the interesting class of compact groups. Because of their large number (the catalogue contains 377 entries) we are able to study the groups in different stages of evolution. Here we give the results of detailed study of four groups, ShCG 154, ShCG 166, ShCG 328 and ShCG 360. We present the redshifts of individual galaxies in groups, the results of the surface photometry in BVR, the contourplots of the surface brightness versus effective radius of galaxies, the twisting postion angle versus effective radius of galaxies, the radial velocity dispersions, the crossing times, the mass-to-luminosity ratios of groups and the results of the X-ray study. The dynamical state of groups, interactions between member galaxies, and the physical parameters of groups are discussed.

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“…The space density of many of ShCGs reaches about 10 4 −10 5 galaxies per Mpc 3 . The groups have a "cigar"-like, prolate spheroid configuration (Oleak et al 1995). Numerical N-body simulations have showen that compact groups should undergo fast dynamical evolution, which will result in coalescence of member galaxies to one giant elliptical galaxy (Barnes 1985(Barnes , 1989Mamon 1986;Bode et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Shakhbazian compact galaxy groups

Tovmassian

Tiersch²,

Chavushyan

et al. 2005

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Abstract. We present the results of a detailed spectroscopic and photometric study of four Shakhbazian compact groups: ShCG 8, ShCG 14, ShCG 19, and ShCG 22. We determined the redshifts of member galaxies and radial velocity dispersions of groups. We also studied the distribution of the surface brightness of member galaxies in R and determined their morphological types. The profiles of the surface brightness versus semi-major axis, the curves of isophotal twisting, and Fourier parameter a 4 are constructed. We found that some members of groups are in the process of interaction. We determined physical parameters of groups: virial masses, luminosities, mass-to-luminosity ratios, and the crossing times. On the basis of the results obtained in this and our previous works, the general properties of 22 ShCGs are discussed.Key words. galaxies: clusters: general -galaxies: distances and redshifts -galaxies: interactions -galaxies: generalgalaxies: kinematics and dynamics -galaxies: photometry IntroductionIn 1995 we commenced a spectroscopic and detailed photometric study of Shakhbazian compact groups (ShCGs). The list of ShCGs contains 377 groups (Shakhbazian 1973;Petrosian 1974Petrosian , 1978Baier et al. 1974;Baier & Tiersch 1975, 1976a, 1976b, 1978, 1979. ShCGs were found by an eye inspection of the POSS prints. They were selected as dense groups of mainly red galaxies, the images of many of which were often hard to distinguish from those of stars. Through follow-up spectral observations (Tiersch et al. 2002, hereafter Paper I;Tovmassian et al. 2003a, hereafter Paper II, 2003b, hereafter Paper III, 2004a, hereafter Paper IV, 2004b, hereafter Paper V) it was found that some objects in the area of groups which were assumed in original papers to be stars, are in reality galaxies. On the other hand, only a Figures 1 and 3-10 are only available in electronic form at http://www.edpsciences.org few assumed members of ShCGs turned out to be stars. Hence, the great majority of the assumed members of these groups are galaxies.Many ShCGs, like ShCG 19 and ShCG 38 (Fig. 1), are very dense formations. Probably due to the compactness of images of the member galaxies, which on the POSS prints are almost indistinguishable from those of stars, these two groups and also some others were missed in other compact group lists, e.g. HCG list (1982). ShCGs generally consist of up to 15 members, while the distances between member galaxies are typically 3−5 times their diameters. The space density of many of ShCGs reaches about 10 4 −10 5 galaxies per Mpc 3 . The groups have a "cigar"-like, prolate spheroid configuration (Oleak et al. 1995). Numerical N-body simulations have showen that compact groups should undergo fast dynamical evolution, which will result in coalescence of member galaxies to one giant elliptical galaxy (Barnes 1985(Barnes , 1989Mamon 1986;Bode et al. 1993). It means that processes of dynamical Article published by EDP Sciences and available at http://www.edpsciences.org/aa or http://dx

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On the ellipticity of the Shakhbazian compact groups of galaxies

Cited by 31 publications

References 0 publications

Shakhbazian compact groups: Poor clusters of galaxies

Shakhbazian compact groups: Poor clusters of galaxies

Shakhbazian compact galaxy groups

Shakhbazian compact galaxy groups

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