E. Branchini et al., RECONSTRUCTING POSITIONS AND PECULIAR VELOCITIES OF GALAXY CLUSTERS WITHIN 25,000 KILOMETERS PER SECOND - THE BULK VELOCITY, The Astrophysical journal, 461(1), 1996, pp. 17-20
Using a dynamical three-dimensional reconstruction procedure, we estim
ate the peculiar velocities of R greater than or equal to 0 Abell/ACO
galaxy clusters from their measured redshift within 25,000 km s(-1). T
he reconstruction algorithm relies on the linear gravitational instabi
lity hypothesis, assumes linear biasing, and requires an input value o
f the cluster beta-parameter (beta(c) = Omega(0)(0.6)/b(c)), which we
estimated in Branchini & Plionis to be beta(c) similar or equal to 0.2
1. The resulting cluster velocity field is dominated by a large-scale
streaming motion along the Perseus-Pisces/Great Attractor baseline dir
ected toward the Shapley concentration, in qualitative agreement with
the galaxy velocity field on smaller scales. Fitting the predicted clu
ster peculiar velocities to a dipole term, in the Local Group frame an
d within a distance of similar to 18,000 km s(-1), we recover extremel
y well both the Local Group velocity and direction, in disagreement wi
th the Lauer & Postman observation. However, we find a similar to 6% p
robability that their observed velocity field could be a realization o
f our corresponding one, if the latter is convolved with their large d
istance-dependent errors. Our predicted cluster bulk velocity amplitud
e agrees well with that deduced by the POTENT and the da Costa et al.
analyses of observed galaxy motions at similar to 5000-6000 km s(-1);
it decreases thereafter, while, at the Lauer & Postman limiting depth
(similar to 15,000 km s(-1)), its amplitude is similar to 150 km s(-1)
, in comfortable agreement with most cosmological models.