Internal dynamics of Abell 2294: a massive, likely merging cluster
  The mechanisms giving rise to diffuse radio emission in galaxy clusters, and
in particular their connection with cluster mergers, are still debated. We aim
to obtain new insights into the internal dynamics of the cluster Abell 2294,
recently shown to host a radio halo. Our analysis is mainly based on redshift
data for 88 galaxies acquired at the Telescopio Nazionale Galileo. We also use
new photometric data acquired at the Isaac Newton Telescope and X-ray data from
the Chandra archive. We re-estimate the redshift of the large, brightest
cluster galaxy (BCG) obtaining <z>=0.1690. We estimate a quite large LOS
velocity dispersion sigma_V about 1400 km/s and X-ray temperature T_X about 10
keV. Our optical and X-ray analysis detects evidence for substructure. Our
results are consistent with the presence of two massive subclusters separated
by a LOS rest frame velocity difference V_rf about 2000 km/s, very closely
projected in the plane of sky along the SE-NW direction. The observational
picture, interpreted through the analytical two-body model, suggests that Abell
2294 is a cluster merger elongated mainly in the LOS direction and catched
during the bound outgoing phase, a few fractions of Gyr after the core
crossing. We find Abell 2294 is a very massive cluster with a range of M=2-4
10E15 M_sun. Moreover, contradicting previous findings, our new data do exclude
the presence of the H$\alpha$ emission in the spectrum of the BCG galaxy. The
outcoming picture of Abell 2294 is that of a massive, quite "normal" merging
cluster, as found for many clusters showing diffuse radio sources.
