The puzzling merging cluster Abell 1914: new insights from the
  kinematics of member galaxies
  We analyze the dynamical state of Abell 1914, a merging cluster hosting a
radio halo, quite unusual for its structure. Our study considers spectroscopic
data for 119 galaxies obtained with the Italian Telescopio Nazionale Galileo.
We select 89 cluster members from spatial and velocity distributions. We also
use photometry Canada-France-Hawaii Telescope archives. We compute the mean
cluster redshift, <z>=0.168, and the velocity dispersion which shows a high
value, sigma_v=1210_{-110}^{+125} km/s. From the 2D analysis we find that Abell
1914 has a NE-SW elongated structure with two galaxy clumps, that mostly merge
in the plane of the sky. Our best, but very uncertain estimate of the velocity
dispersion of the main system is sigma_v~1000 km/s. We estimate a virial mass
M_sys=1.4--2.6 10^{15} h_{70}^{-1} Msun for the whole system. We study the
merger through a simple two-body model and find that data are consistent with a
bound, outgoing substructure observed just after the core crossing. By studying
the 2D distribution of the red galaxies, photometrically selected, we show that
Abell 1914 is contained in a rich large scale structure, with two close
companion galaxy systems, known to be at z~0.17. The system at SW supports the
idea that the cluster is accreting groups from a filament aligned in the NE-SW
direction, while that at NW suggests a second direction of the accretion NW-SE.
We conclude that Abell 1914 well fits among typical clusters with radio halos.
We argue that the unusual radio emission is connected to the complex cluster
accretion and suggest that Abell 1914 resembles the well-known nearby merging
cluster Abell 754 for its particular observed phenomenology.
