The Shape of the Dark Halo in Polar-Ring Galaxies

Photometric and kinematic observations of the polar-ring galaxies NGC 4650A and ESO 415-G26 are presented. The inner component of each system is an S0 galaxy, as was previously found in the case of A0136-0801. A comparison of the circular velocity in the S0 component with the rotation velocity in the polar ring indicates that the halo of dark matter is nearly spherical; the mean value of V(Ring)/V(disk) for the three galaxies is 0.97 + or - 0.08. Estimates for the flattening of equipotentials in the galaxies are 0.86 + or - 0.21, 1.05 + or - 0.17, and 0.98 + or - 0.20. CCD images of both NGC 4650A and ESO 415-G26 show faint disordered nebulosity in the outer regions, suggestive of tidal debris. This provides further evidence that the polar rings in these systems resulted from 'second events' which may have been mergers of two galaxies or near collisions with resultant mass transfers.