Photometry and Spectroscopy of Elliptical Galaxies. V. Galaxy Streaming toward the New Supergalactic Center

We analyze here the dynamics of 400 elliptical galaxies of our all-sky survey. The motions of the elliptical galaxies, over and above Hubble expansion in the Cosmic Microwave Background (CMB) frame, are best fitted by a flow toward a great attractor centered on l = 307, b = 9 at a distance of R_m_ = 4350 +/- 350 km s^-1^ in the Hubble flow. The excess mass must be ~5.4 x 10^16^ M_sun_, comparable to the largest superclusters in order to generate the streaming motion at the Sun of 570 +/- 60 km s^-1^. This model, which is an enlarged version of that considered earlier by Shaya, Tammann, and Sandage, and Lilje, Yahil, and Jones, gives a much better fit to the motions of the ellipticals than the bulk motion considered earlier. The latter was itself a much better fit than pure Hubble flow in the CMB frame. A picture of the hemisphere of sky centered on this direction shows a remarkable concentration of galaxies that broadens the supergalactic band near there (see Fig. 8 in main text). Estimates show that this concentration in Centaurus is some 20 times more populous than the Virgo cluster, although the southern part of the concentration may be obscured by dust in the Milky Way. The Centaurus concentration is behind the big clusters of ellipticals in Centaurus which show large peculiar motions toward it. The Centaurus concentration both gives more light here and generates more "infall" velocity here than the Virgo cluster, although the latter is at one-third the distance. Because the Centaurus concentration evidently dominates the supergalactic band of galaxies, we suggest that it be called the supergalactic center. Da Costa et al. have published a redshift survey in the direction of the concentration. It shows a strong peak in galaxies with mean heliocentric redshift of 4355 +/- 124 km s^-1^ and with a velocity dispersion of 1052 km s^-1^; transforming to the CMB frame here, the mean velocity is 4654 +/- 124 km s^-1^, in surprisingly good agreement with our totally independent estimate from the motions of ellipticals all around the sky. In the far field, away from Centaurus, we find a negligible streaming, in agreement with the earlier result of Aaronson et al. The value of {OMEGA}_0_ from these observations is still indeterminate, though higher values near unity are somewhat more compatible than low values. A structure as large as the supercluster could cause a measurable {DELTA}T/T in the microwave background on scales of 0.1^deg^-1^deg^, especially if {OMEGA}_0_ is as low as 0.2. Comparison of the observed flow velocities with the cold dark matter model suggests that cold dark matter with biasing parameter b=1 is marginally consistent with the motions, but that b >= 2 is not.