The puzzling merging cluster Abell 1914: new insights from the kinematics of member galaxies

We analyse 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, σV = 1210{^{+ 125}_{- 110}} km s-1. From the 2D analysis we find that Abell 1914 has a north-east (NE)-south-west (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 σV, main ˜ 1000 km s-1. We estimate a virial mass Msys = 1.4-2.6 × 1015 h{^{- 1}_{70}} 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 haloes. 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.