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The motions of clusters and group of galaxiesThe distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard cold dark matter (CDM) (omega = 1); low-density CDM (omega = 0.3); hot dark matter (HDM) (omega = 1); and primeval baryonic isocurvature (PBI) (omega = 0.3). All models are normalized to the microwave background fluctuations observed by Cosmic Background Explorer (COBE). We find that rich clusters of galaxies exhibit a Maxwellian distribution of peculiar velocities in all models, as expected from a Gaussian initial density field. The clusters appear to be fundamental and efficient tracers of the large-scale velocity field. The cluster three-dimensional velocity distribution typically peaks at v approximately 600 km/s and extends to high cluster velocities of v approximately 2000 km/s. The low-density CDM model exhibits somewhat lower velocities: it peaks at approximately 400 km/s and extends to approximately 1200 km/s. Approximately 10% (approximately 1% for low-density CDM) of all model rich clusters move with high peculiar velocities of V greater than or = 10(exp 3) km/s. The highest velocity clusters frequently originate in dense superclusters. The model velocity distributions of rich clusters are compared with the model velocity distributions of small groups of galaxies, and of the total matter. The group velocity distribution is, in general, similar to the velocity distribution of the rich clusters. The matter velocity distribution is similar to that of the rich clusters for the omega = 0.3 models; these models exhibit Maxwellian velocity distributions for clusters, for groups, and for matter that are all similar to one another. The mass distribution in the omega = 1 models, however, exhibits a longer tail of high velocities than do the clusters. This high-velocity tail originates mostly from the high velocities that exist within rich clusters. The model velocity distributions of groups and clusters of galaxies are compared with observations. The data exhibit a larger high-velocity tail, to v(sub r) greater than or = 2000 km/s, than is seen in the model simulations (except for HDM). Because of the large observational uncertainties, however, the data are consistent at a approximately 1-3 sigma level with the model predictions and with a Gaussian initial density field. Accurate observations of cluster peculiar velocities, especially at the high-velocity tail, shoud provide powerful constraints on the cosmological models.
Document ID
19950037113
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bahcall, Neta A.
(Princeton Univ. Observatory, Princeton, NJ, United States)
Gramann, Mirt
(Princeton Univ. Observatory, Princeton, NJ, United States)
Cen, Renyue
(Princeton Univ. Observatory, Princeton, NJ, United States)
Date Acquired
August 16, 2013
Publication Date
November 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 436
Issue: 1
ISSN: 0004-367X
Subject Category
Astrophysics
Accession Number
95A68712
Funding Number(s)
CONTRACT_GRANT: NSF AST-90-20506
CONTRACT_GRANT: NSF ASC-93-18185
CONTRACT_GRANT: NSF AST-91-08103
CONTRACT_GRANT: NSF AST-93-15368
CONTRACT_GRANT: NAGW-2448
Distribution Limits
Public
Copyright
Other

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