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Astron. Astrophys. 337, 17-24 (1998)

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4. Summary

We have presented the results of a redshift survey in an area between the Abell clusters A 548 and A 3367. These two clusters have been suspected to be a close pair and therefore candidates to undergo a merging process.

We obtained 180 new galaxy velocities with the use of multifiber spectroscopy, [FORMULA] of which presents emission lines. The redshift histogram shows clearly three peaks at [FORMULA] km/s, [FORMULA] km/s and [FORMULA] km/s: for each of them we have estimated the dynamical parameters.

The first structure (peak A) is at the velocity of A 548 and could be considered as an extension of this cluster. In particular, this peak is formed by two substructures, corresponding to two subclusters in A 548 revealed by Davis et al. (1995) both in the optical distribution of galaxies and in a ROSAT X-ray map. The velocity dispersions of our two clumps in peak A are significantly smaller than those determined in the subclumps of Davis et al., while the mean velocities are in agreement.

Peak B has [FORMULA] km/s and a velocity dispersion of [FORMULA] km/s; the distribution of its members on the plane of the sky corresponds to the highest density excess of A 3367: for this reason we suggest that the name A 3367 should be attributed to this clump. The mean velocity reported for A 3367 by Postman et al. (1992) is based on galaxies belonging to peak A, and therefore to an extension of A 548 rather than to A 3367.

Our general conclusion is that A 548 and A 3367 is not a close pair of merging clusters, as the two structures have a significantly different redshift. However, we found that the complex dynamical structure of A 548 has large coherence, with a projected extension in the range of 1-3 h-1 Mpc.

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© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998