Dynamics of Abell 3266-I. An optical view of a complex merging cluster

We present spectroscopy of 880 galaxies within a 2 degrees field around the massive, merging cluster Abell 3266. This sample, which includes 704 new measurements, was combined with the existing redshifts measurements to generate a sample of over 1300 spectroscopic redshifts; the largest spectroscopic sample in the vicinity of A3266 to date. We define a cluster sub-sample of 790 redshifts that lie within a velocity range of 14 000 to 22 000 km s(-1) and within 1 degrees of the cluster centre. A detailed structural analysis finds A3266 to have a complex dynamical structure containing six groups and filaments to the north of the cluster as well as a cluster core that can be decomposed into two components split along a northeast-southwest axis, consistent with previous X-ray observations. The mean redshift of the cluster core is found to be 0.0594 +/- 0.0005 and the core velocity dispersion is given as 1462(-99)(+99) km s(-1). The overall velocity dispersion and redshift of the entire cluster and related structures are 1337(-67)(+67)km s(-1) and 0.0596 +/- 0.0002, respectively, though the high velocity dispersion does not represent virialized motions but rather is due to relative motions of the cluster components. We posit A3266 is seen following a merger along the northeast-southwest axis; however, the rich substructure in the rest of the cluster suggests that the dynamical history is more complex than just a simple merger with a range of continuous dynamical interactions taking place. It is thus likely that turbulence in A3266 is very high, even for a merging cluster.