Using a dynamical three-dimensional reconstruction procedure, we estimate 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). The reconstruction algorithm relies on the linear gravitational instability hypothesis, assumes linear biasing, and requires an input value of 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 0.21. The resulting cluster velocity field is dominated by a large-scale streaming motion along the Perseus-Pisces/Great Attractor baseline directed toward the Shapley concentration, in qualitative agreement with the galaxy velocity field on smaller scales. Fitting the predicted cluster peculiar velocities to a dipole term, in the Local Group frame and within a distance of similar to 18,000 km s(-1), we recover extremely well both the Local Group velocity and direction, in disagreement with the Lauer & Postman observation. However, we find a similar to 6% probability that their observed velocity field could be a realization of our corresponding one, if the latter is convolved with their large distance-dependent errors. Our predicted cluster bulk velocity amplitude 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.

Reconstructing positions and peculiar velocities of galaxy clusters within 25,000 kilometers per second: The bulk velocity

Branchini E;
1996

Abstract

Using a dynamical three-dimensional reconstruction procedure, we estimate 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). The reconstruction algorithm relies on the linear gravitational instability hypothesis, assumes linear biasing, and requires an input value of 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 0.21. The resulting cluster velocity field is dominated by a large-scale streaming motion along the Perseus-Pisces/Great Attractor baseline directed toward the Shapley concentration, in qualitative agreement with the galaxy velocity field on smaller scales. Fitting the predicted cluster peculiar velocities to a dipole term, in the Local Group frame and within a distance of similar to 18,000 km s(-1), we recover extremely well both the Local Group velocity and direction, in disagreement with the Lauer & Postman observation. However, we find a similar to 6% probability that their observed velocity field could be a realization of our corresponding one, if the latter is convolved with their large distance-dependent errors. Our predicted cluster bulk velocity amplitude 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.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11567/1072567
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