Studies of the Cluster Abell 2634

Structure and Kinematics of Abell 2634

Using a redshift database that includes newly obtained optical and HI line spectra for 663 galaxies with known redshifts in a 6deg by 6deg field centered on A2634, we find six main galaxy concentrations: the nearby clusters A2634 and A2666, two groups in the vicinity of A2634, and two distant clusters at ~18,000 (A2622) and ~37,000 kms seen in projection near the core of A2634. We show that early-type galaxies appear to be a relaxed system, while the spiral population eschews the center of the cluster and exhibits both a multimodal velocity distribution and a much larger velocity dispersion than the ellipticals. We propose that the spiral galaxies of A2634 represent a dynamically young cluster population.

For the galaxy component of A2634, we find no evidence of significant substructure in the central regions. We also conclude that the adoption of leni ent membership criteria that ignore the dynamical complexity of A2634 are unlike ly to be responsible for the conflicting results reported on the motion of this cluster with respect to the CMB.

A Large HI Cloud in Abell 2634

In addition, we reported the serendipitous discovery of a large HI cloud with an associated HI mass of 6 +/-1.5 X 10**9 h**2 solar masses and a heliocentric velocity 8800 km/s, located near the periphery of Abell 2634. Its velocity field appears to be very quiescent, as no gradients in the peak velocity are seen over its extent of 143 X 103 kpc. The distribution of gas is poorly resolved spatially, and it is thus difficult at this time to ascertain the nature of the cloud. At least two relatively small, actively star--forming galaxies appear to be embedded in the HI gas, which may (a) be an extended gaseous envelope surrounding one or both galaxies, (b) have been spread over a large region by a severe episode of tidal disruption or (c) have been affected by the ram pressure resulting from its motion through the intracluster gas of A2634.

The Distance to Abell 2634

We have used the Tully Fisher and Fundamental Plane relations to derive the distances to both the Coma and Abell 2634 clusters. This was part of the thesis work of Marco Scodeggio.

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