HCGs: stable and rotating systems?

✍ Scribed by H.M. Tovmassian

• Book ID: 101379369
• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 135 KB
• Volume: 323
• Category: Article
• ISSN: 0004-6337
• DOI: 10.1002/1521-3994(200210)323:5<488::aid-asna488>3.0.co;2-2

✦ Synopsis

It is shown that the radial velocity dispersion of the elongated HCGs ( ¼ ¾

) with smaller two-dimensional galaxy-galaxy median projected separation Ê is, on average, higher than those of the groups with larger Ê . It shows that galaxies in a group move preferentially along its elongation. Inspection of radial velocities of member galaxies in chain-like and in roundish HCGs shows that galaxies in HCGs most probably rotate around the gravitational center of the corresponding group. Other two possible mechanisms: flying apart of galaxies from the group in opposite directions, and infall of field galaxies upon the group are excluded. It follows that HCGs are, probably, more stable formations, than it has been assumed. In this case the known inconsistencies between the results of the N-body simulations and the observational facts are being excluded.