Photometric and spectroscopic study of the Shakhbazian compact galaxy groups ShCG 254, ShCG 257, ShCG 351, and ShCG 371

Abstract

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Photometric observations of nine Shakhbazian compact groups

“…A large number of interacting galaxies are detected among ShCG members [14,[15][16][17][18][19][20][21][22][23]. A large number of interacting galaxies are detected among ShCG members [14,[15][16][17][18][19][20][21][22][23].…”

“…Spectral and photographic observations of a large number of ShCG groups have been made by Tiersch et al [14 and references therein] and Tovmassian et al [15][16][17][18][19][20][21][22][23]. It was shown that the majority of the candidate group members were galaxies with accordant radial velocities (usually < 1000 km s -1 ).…”

The properties of the heterogeneous Shakhbazyan groups of galaxies in the SDSS

“… Comparison between our spectroscopic size estimates of the SHK groups and those performed by Tovmassian et al (1999–2007) (plain dots), Tiersch et al (1994–2002) (diamonds) and Kirshner & Malumuth (1980) (asterisks)(upper panel). Similarly, in the lower panel, our size estimates of the HCGs are compared with those performed by Hickson (1982) and Hickson et al (1992).…”

“…Our size estimates are consistent with the HCGs sizes for ∼50 per cent of the sample . For the SHK sample, where sizes calculated according to photometric criteria are not available in literature, we compare with the virial radii of the groups measured by Tovmassian et al (1999–2007) and Tiersch et al (1994–2002). According to Tovmassian et al (2005c), the virial radii generally do not exceed ≈ 160 kpc, while the mean mass‐weighted radial velocity dispersion is 330 ± 170 km s −1 (Tovmassian et al 2007), ranging from 88.5 to 667.1 km s −1 , thus implying dynamical crossing times varying from 2.7 × 10 7 to 1.9 × 10 8 yr (Tovmassian et al 2005c, 2007), on an average shorter than what found for the HCGs ≈ 2.1 × 10 8 yr (Hickson et al 1992).…”

“…Furthermore, even though some contamination by stars is indeed present, many of the objects initially suspected to be stars were found to be galaxies. The extensive and detailed studies by Tiersch, (Tiersch 1976; Tiersch et al 1993, 1994, 1995, 1996a, 1996a,b, 2002), Tovmassian (Tovmassian et al 1998, 1999a,b; Tovmassian & Tiersch 2001; Tovmassian et al 2003a,b, 2004, 2005a,b,c, 2006, 2007) and collaborators of a subset of 44 groups have shown that SHK groups form a rather intriguing class of physically bound and moderately compact structures. The spatial densities of SHK groups found in these works, span a wide range: from slightly higher than those of loose groups (10–10 2 gal Mpc −3 ) up to values comparable to the cores of rich clusters or HCGs (10 4 – 10 5 gal Mpc −3 ) for m ≲ 19 mag.…”