Starting from the observed distribution of Abell/ACO galaxy clusters in redshift space, we use a two-step procedure to recover their distances and peculiar velocities. After statistically correcting for the unobserved cluster distribution in the zone of avoidance and also for a smooth absorption at higher latitudes, we use a dynamical iterative algorithm, based on that published by Strauss & Davis in 1988, to recover the real-space duster positions by minimizing the redshift-space distortions. The whole procedure assumes that clusters trace the mass, that peculiar velocities are caused by gravity, and that linear perturbation theory applies. The amplitude of the cluster dipole measured in real space turns out to be similar to 23% less than that measured in redshift space. In both cases the dipole direction is aligned with the cosmic microwave background dipole within similar to 10 degrees, taking into account the Virgocentric infall component of the Local Group motion. Using linear theory we obtain beta(c)(=Omega(0)(0.6)/b(c)) approximate to 0.21(+/-0.03), where the uncertainty is due to observational errors and limitations in the reconstruction procedure, while the intrinsic cosmological variance amounts to similar to 0.07. This beta(c) value implies that for a cluster-mass bias parameter of b(c) less than or similar to 5, a flat universe is not excluded, contrary to previous cluster-dipole z-space analysis. A more stringent determination of beta(c) will be obtained from the analysis of the peculiar velocity field in a forthcoming paper.

Reconstructing positions and peculiar velocities of galaxy clusters within 25,000 kilometers per second: The cluster real space dipole

BRANCHINI, ENZO FRANCO;
1996

Abstract

Starting from the observed distribution of Abell/ACO galaxy clusters in redshift space, we use a two-step procedure to recover their distances and peculiar velocities. After statistically correcting for the unobserved cluster distribution in the zone of avoidance and also for a smooth absorption at higher latitudes, we use a dynamical iterative algorithm, based on that published by Strauss & Davis in 1988, to recover the real-space duster positions by minimizing the redshift-space distortions. The whole procedure assumes that clusters trace the mass, that peculiar velocities are caused by gravity, and that linear perturbation theory applies. The amplitude of the cluster dipole measured in real space turns out to be similar to 23% less than that measured in redshift space. In both cases the dipole direction is aligned with the cosmic microwave background dipole within similar to 10 degrees, taking into account the Virgocentric infall component of the Local Group motion. Using linear theory we obtain beta(c)(=Omega(0)(0.6)/b(c)) approximate to 0.21(+/-0.03), where the uncertainty is due to observational errors and limitations in the reconstruction procedure, while the intrinsic cosmological variance amounts to similar to 0.07. This beta(c) value implies that for a cluster-mass bias parameter of b(c) less than or similar to 5, a flat universe is not excluded, contrary to previous cluster-dipole z-space analysis. A more stringent determination of beta(c) will be obtained from the analysis of the peculiar velocity field in a forthcoming paper.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11567/1072858
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 28
  • ???jsp.display-item.citation.isi??? 30
social impact