Alignment effects in clusters of galaxies

Abstract

We present the measurement of 204 position angles of the brightest cluster galaxies in a sample of southern clusters (Abell, Corwin and Ollowing 1989). We analyze cluster-cluster alignment effects in this sample and extend it with previous sample of Abell clusters in the northern hemisphere. Binggeli's (1982) test is used with distances derived from the log(cz-m₁₀) giving an alignment signal consistent with redshift derived distances. Our results suggest a weak but statistically significant signal of alignment of the brightest galaxy in a cluster with the projected vector toward the nearest approximately to a 30% excess of brightest cluster galaxies pointing to the nearest cluster of galaxies. The mean acute angle between the galaxy position angle and the direction towards the nearest neighbor is = 39°±2°, or less. The scale of the detected anisotropy is D=15 Mpc/h. The statistical results are controlled by means of Montecarlo simulations and several points concerning the cluster-cluster alignment effects are discussed.Asociación Argentina de Astronomí

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