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1. Introduction

  Ever since the pioneering work of Abell (1958), it has been realized that the study of clusters of galaxies holds great promise of providing clues to several fundamental problems in Cosmology. The global properties and the internal structure of clusters contain information about their formation and evolution and therefore, indirectly, about several of the parameters of the scenario for the formation of large-scale structure. At this moment cluster properties are determined from essentially four types of observation: the projected galaxy distribution, the kinematics of the cluster galaxies, the distribution of the density and temperature of the hot X-ray emitting gas and, finally, the surface density of the total gravitating mass (galaxies, gas and dark matter) as derived from gravitational lensing.

In the late seventies the first systematic cluster redshift surveys were made for the nearest and most conspicuous clusters, such as Coma (e.g. Kent & Gunn 1982). In the early eighties, the first extensive cluster redshift surveys were done of samples of rich clusters, for each of which, on average, of order 100 redshifts were obtained (e.g. Dressler & Shectman 1988). These redshift surveys used galaxy catalogues of cluster member candidates especially prepared for these clusters (e.g. the photometric catalogue by Godwin & Peach 1977, for the Coma cluster, or the catalogues by Dressler 1980, used by Dressler & Shectman).

Most of the early redshift work on clusters employed slit-spectroscopy of individual galaxies. However, several kinds of multi-object spectrographs have become available in the last ten years or so. This has accelerated cluster redshift surveys by factors between, say 10 and 100. As a result, extensive redshift surveys for large samples of clusters have become possible. This allows a detailed study of the dynamics of galaxy clusters as a species, from a combination of kinematical data with surface density profiles, X-ray data and evidence from lensing. By themselves, the redshift surveys also enable one to study possible kinematical differences between different types of cluster galaxies, and structure in the phase space of clusters, both of which may give important clues about the formation and dynamical evolution of clusters.

At ESO, the Optopus multi-object fibre spectrograph was developed in the mid eighties (see e.g. Lund 1986 or Avila et al. 1989). It employs aperture plug plates at the Cassegrain focus of the 3.6-m telescope. With its aperture plate size of tex2html_wrap_inline1415 it was ideally suited to redshift surveys of the central regions of rich and not-too-nearby clusters. In this paper, we present the redshift catalogue that has resulted from a survey with the Optopus spectrograph of about 100 rich southern clusters in the redshift range from tex2html_wrap_inline14170.04 to tex2html_wrap_inline14170.1. The spectroscopic observations took place during about 35 nights in 9 observing runs in the period September 1989 to October 1993.

We have already discussed several aspects of the observations and the data analysis of the survey which has resulted in the catalogue that we present here (see Katgert et al. 1996, Paper I), and which we will refer to as the ENACS catalogue. We have also discussed several results based on the ENACS catalogue, e.g. the distribution of the velocity dispersions of a volume-limited complete sample of rich Abell clusters (Mazure et al. 1996, Paper II), and the kinematics of emission-line galaxies (Biviano et al. 1997, Paper III). In addition, the ENACS data have also been used to study the kinematics and dynamics of the galaxies in the cores of rich clusters (den Hartog & Katgert 1996; den Hartog 1997).

A few other papers have been submitted, e.g. on the Fundamental Plane of clusters (Adami et al. 1997), on the density profiles of clusters (Adami et al. 1998) and on the distribution and kinematics of early- and late-type galaxies (de Theije & Katgert 1998). We are also working on several other aspects of the structure and dynamics of rich clusters, using the ENACS as a starting point. In addition, other groups have already used some of the ENACS data e.g. to make an independent study of the distribution of cluster velocity dispersions (Fadda et al. 1996), to study substructure in the distribution of the cluster galaxies (Girardi et al. 1997), and to construct the power spectrum on large scales (Borgani et al. 1997). Here, we present the total ENACS catalogue to enable other workers in the field to take full advantage of all aspects of our dataset.


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