  The Abell 1689 galaxy cluster has recently become a subject of intensive
study. Thanks to its intermediate redshift (z=0.183) its mass distribution can
be reconstructed using numerous methods including gravitational lensing, galaxy
kinematics and X-ray imaging. The methods used to yield conflicting mass
estimates in the past and recently the cluster mass distribution has been
claimed to be in conflict with standard CDM scenarios due to rather large
concentration and steep mass profile obtained from detailed studies of
Broadhurst et al. using lensing. By studying in detail the kinematics of about
200 galaxies with measured redshifts in the vicinity of the cluster we show
that the cluster is probably surrounded by a few structures, quite distant from
each other, but aligned along the line of sight. We support our arguments by
referring to cosmological N-body simulations and showing explicitly that
distant, non-interacting haloes can produce entangled multi-peak line-of-sight
velocity distributions similar to that in A1689. We conclude that it is
difficult to estimate the cluster mass reliably from galaxy kinematics, but the
value we obtain after applying a simple cut-off in velocity agrees roughly with
the mass estimated from lensing. The complicated mass distribution around the
cluster may however increase the uncertainty in the determination of the
density profile shape obtained with weak lensing.
