2005MNRAS.359.1491K

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 disc-like model of a cluster. Galaxies from cumulative subsamples containing more and more distant members from the cluster centre are projected on to 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 that rotational effects are more strongly expressed at distances of 0.26-0.54 Mpc from the cluster centre. The total virial mass of the cluster is (3.2±0.6)x10¹⁴M_☉, while the virial mass, corrected for rotation, is (2.8±0.5)x10¹⁴M_☉.