Abstract
We determine the velocity correlation function, pairwise peculiar velocity difference, and rms pairwise peculiar velocity dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Ω = 1 and Ω ;= 0.3 cold dark matter (CDM), and Ω = 0.3 primeval baryonic isocurvature (PBI) models (all flat and COBE-normalized). We find that close cluster pairs, with separation r < 10 h-1 Mpc, exhibit strong attractive peculiar velocities in all models; the cluster pairwise velocities depend sensitively on the model. The mean pairwise attractive velocity of clusters on 5 h-1 Mpc scale ranges from ∼1700 km s-1 for Ω = 1 CDM to ∼1000 km s-1 for PBI to ∼700 km s-1 for Ω = 0.3 CDM. The small-scale pairwise velocities depend also on cluster mass: richer, more massive clusters exhibit stronger attractive velocities than less massive clusters. On large scales, from ∼20 to 200 h-1 Mpc, the cluster peculiar velocities are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster velocity correlation function is negative on small scales for Ω = 1 and Ω = 0.3 CDM, indicating strong pairwise motion relative to bulk motion on small scales; PBI exhibits relatively larger bulk motions. The cluster velocity correlation function is positive on very large scales, from r ∼ 10 h-1 Mpc to r ∼ 200 h-1 Mpc, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to ∼200 h-1 Mpc. The strong dependence of the cluster velocity functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.
Original language | English (US) |
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Pages (from-to) | L51-L54 |
Journal | Astrophysical Journal |
Volume | 437 |
Issue number | 1 PART 2 |
DOIs | |
State | Published - Dec 10 1994 |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Keywords
- Cosmology: theory
- Galaxies: clustering
- Galaxies: clusters of
- Large-scale structure of universe