Part of VV 116. In a remarkable nest -- dense group of five galaxies. Photo: VV Atlas No. 116 and Ap J 134, 248, where the Burbidges give redshifts: MCG -01-25-009 = a = A: E +6356 MCG -01-25-010 = e = B: E +6576 (MCG -01-25-008 = c)? = C: S +6631 H{alpha} and {lambda} 6583 and 6548 [N II]. (MCG -01-25-012 = d)? = D: S +6630 H{alpha}, defined rotation and mass. In the tables: our notation in the photo and VV Atlas is given with lower-case letters, and the upper-case letters is the Burbidges' notation. 3. VV 116 Group This quintet was discovered by Vorontsov-Velyaminov (1960) and it has been investigated by us (Burbidge and Burbidge 1959b, 1961b; photographs are published in both references). It is a compact group of two ellipticals and three spirals, and a narrow fairly bright filament that runs between the fainter of the two of the spirals. This filament might alternatively be a faint sixth member of the group. Magnitudes are not available for these galaxies, but we have named them A-E in order of decreasing apparent brightness on our plates. Velocities for four of the five members have been obtained, and they are: A (elliptical), +6356+/-40 km/sec; B (elliptical), +6576+/-40 km/sec; C (spiral), +6631+/-30 km/sec; D (spiral), +6230+/-30 km/sec. Spiral C has very strong emission lines; spiral D has less strong emission. For D it was possible to obtain an estimate of the rotation from the tilted H{alpha} emission line. By assuming that the masses of the ellipticals were 10X those of the spirals, and by allowing for the unmeasured galaxy E by multiplying the kinetic energy by 5/4, we found that the virial theorem could be satisfied by masses of 5.5X 10^11^ M_sun_ for the ellipticals and 5.5X 10^10^ M_sun_ for the spirals, i.e., a total mass of 1.3 X 10^12^ M_sun_. Here we can make a direct comparison with the mass of D independently estimated from its rotation; the value thus obtained is 3.3X 10^10^ M_sun_. This value is in sufficiently good agreement with the average value of 5.5 X 10^10^ M_sun_ obtained from the virial theorem for us to conclude that the system is stable, although ultimately, of course, it will suffer the rearrangement of kinetic energy that occurs in trapezium-like systems resulting in disruption of the compact configuration. Two final comments must be made: (i) if galaxy E is found to have a high relative velocity, then the group may still prove to be unstable. (ii) The reason why it appears to be stable on the evidence of the velocities. given above is that the galaxies are very close together - their average three-dimensional separation is only about 37 kpc. The outer regions of at least four of them appear to be interconnected. |