Radio Emission of Shakhbazian Compact Galaxy Groups

This paper presents the results of a pilot redshift survey of 18 candidate compact groups from the distant DPOSS survey that extends to redshift ∼0.2 the available surveys of compact groups of galaxies, mainly Hickson Compact Groups and Southern Compact Groups. The goal of our survey was to confirm group membership via redshift information and to measure the characteristic parameters of a representative, albeit small, sample of DPOSS survey groups. Of the 18 candidates observed, seven are found to be indeed isolated compact groups, i.e. groups with 3 or more concordant members and with no neighbouring known cluster, while 7 are chance projection configurations on the sky. Three remaining candidates, despite having 3 or more concordant member galaxies, are located in the neighbourhood of known clusters, while another candidate turned out to be a dense sub-condensation within Abell 0952. The median redshift of our 7 confirmed groups is z ∼ 0.12, to be compared with a median redshift of 0.03 for the local sample of compact groups by Hickson. The typical group size is ∼50 kpc, and the median radial velocity dispersion is 167 km s 0 , all similar to the values usually found in the literature for such structures in the local universe. The average mass-to-light ratio for our groups, M/L B , is 92h, higher than the value found for nearby Hickson compact groups but lower than that found for loose groups. Our results suggest that, once full redshift information for its members becomes available, the DPOSS sample will provide a reference sample to study the properties of compact groups beyond the local universe.

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“…The quoted redshift is z = 0.130 (Tovmassian et al 1999), while the one we measured is z = 0.1319 ± 0.0002, i.e. ∼600 km s −1 difference.…”

Section: Redshift Measurementscontrasting

confidence: 45%

The DPOSS II compact group survey: first spectroscopically confirmed candidates

Pompei

Carvalho

Iovino

2006

A&A

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“…10. Only a few galaxies in ShCGs have FIR and radio emission (Tovmassian et al 1998(Tovmassian et al , 1999, although according to N-body simulations it is expected that in dense environments of groups the number of interactions and merging will be high; and consequently there should be a high number of radio and FIR emitting galaxies. The absence of strong radio and FIR sources in compact groups may be explained by their large distances and by suggested semiregular oscillation of the group members in elongated orbits around its gravitational center (Tovmassian 2002).…”

Section: Discussionmentioning

confidence: 99%

Shakhbazian compact galaxy groups

Tovmassian

Tiersch²,

Chavushyan

et al. 2005

A&A

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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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“…1), which is a sign of thermal heating (Paper I). Moreover, galaxy 4 has radio emission (Tovmassian et al 1999). Halos of galaxies 15, 3 and 7 located close to the brightest galaxy 1 seem to overlap the halo of the latter, and also each other.…”

Section: Discussionmentioning

confidence: 99%

“…The radio source NVSS J233236+192215 was identified with galaxy 7 or with its close faint neighbour (Tovmassian et al 1999). The spiral arms of galaxy 7 are undisturbed (Fig.…”

Section: Discussionmentioning

confidence: 99%

Shakhbazian compact galaxy groups

Tovmassian¹,

Tiersch²,

Navarro³

et al. 2004

A&A

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Abstract. In 1995 we commenced a detailed spectral and photometric study of Shakhbazian compact groups. In this paper the results on groups ShCG 181, ShCG 344, ShCG 361, and ShCG 362 are presented. The redshifts of member galaxies in groups and the radial velocity dispersions, the results of the surface photometry in BVR, the profiles of the surface brightness versus semi-major axis a (or a 1/4 ) and the twisting position angle versus semi-major axis of galaxies, virial masses, luminosities and mass-to-luminosity ratios, and the crossing times of groups are given. It is shown that some members of groups are in the process of interaction. On the basis of the results obtained in this and previous works, the general properties of thirteen ShCGs are discussed.

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Radio Emission of Shakhbazian Compact Galaxy Groups

Cited by 13 publications

References 49 publications

The DPOSS II compact group survey: first spectroscopically confirmed candidates

The DPOSS II compact group survey: first spectroscopically confirmed candidates

Shakhbazian compact galaxy groups

Shakhbazian compact galaxy groups

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