We present indications of rotation in the galaxy cluster A2107 by a method
that searches for the maximum gradient in the velocity field in a flat
disk-like model of a cluster. Galaxies from cumulative sub-samples containing
more and more distant members from the cluster centre, are projected onto an
axis passing through the centre and we apply a linear regression model on the
projected distances $x$ and the line-of-sight velocities $V$. The axis with the
maximum linear correlation coefficient $r_{max} = \max [ r(V,x) ]$ defines the
direction of the maximum velocity gradient, and consequently it presents the
major axis of the apparently elliptical cluster. Because the effects of
rotation are subtle, we put strong emphasis on the estimation of the
uncertainties of the results by implementing different bootstrap techniques. We
have found the rotational effects are more strongly expressed from distances
$0.26 \div 0.54$ Mpc from the cluster centre. The total virial mass of the
cluster is $(3.2\pm0.6)\times10^{14} {\cal M}_{\sun}$, while the virial mass,
corrected for the rotation, is $(2.8\pm0.5) \times 10^{14}{\cal M}_{\sun}$.Comment: 7 pages, 9 figures gzipped tar file. to be published in MNRA
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