# Dynamics of Abell 3266 - I. An Optical View of a Complex Merging Cluster

## TL;DR

This study provides an extensive optical spectroscopic analysis of Abell 3266, revealing its complex dynamical structure, multiple substructures, and ongoing merger activities, highlighting the turbulent nature of this massive galaxy cluster.

## Contribution

The paper offers the largest spectroscopic redshift sample for A3266 and detailed analysis of its complex dynamical state and substructures, advancing understanding of cluster mergers.

## Key findings

- A3266 contains six groups and filaments north of the core.
- The cluster core has a velocity dispersion of 1462 km/s.
- The overall cluster velocity dispersion is about 1337 km/s, indicating complex dynamics.

## Abstract

We present spectroscopy of 880 galaxies within a 2-degree 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 which lie within a velocity range of 14,000 to 22,000 kms$^{-1}$ and within 1 degree 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 which 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 $0.0594 \pm 0.0005$ and the core velocity dispersion is given as $1462^{+99}_{-99}$ kms$^{-1}$. The overall velocity dispersion and redshift of the entire cluster and related structures are $1337^{+67}_{-67}$ kms$^{-1}$ and $0.0596 \pm 0.0002$, respectively, though the high velocity dispersion does not represent virialised 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.