A Technique for Detecting Structure in Cluster Velocity Distributions
Abstract
For clusters with ≳100 measured galaxy redshifts, we develop a new method for detecting departures from a Gaussian velocity distribution. We decompose the cluster velocity distribution into a sum of the orthogonal Gauss-Hermite functions. This method quantifies the asymmetric third-order (h3) and symmetric fourth-order (h4) terms of the distribution while minimizing the effect of interlopers in the tails.
We apply the method to a sample of eight rich clusters: A426, A548, At060, Al 656, A2151, A2670, DC 2048-52, and Centaurus. Each cluster has more than 100 members with known redshifts. The clusters A548, Al 656, DC 2048-52, and Centaurus significantly depart from Gaussian. A1656 and DC 2048-52 have asymmetric velocity distributions; A548 and Centaurus have broad, symmetric distributions. The most likely interpretation is that these systems have substructure. This result is consistent with findings by other authors.- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1993
- DOI:
- 10.1086/173457
- Bibcode:
- 1993ApJ...419...47Z
- Keywords:
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- GALAXIES: CLUSTERING;
- GALAXIES: DISTANCES AND REDSHIFTS