I will present the new results
on the dark halo shape around Polar Ring Galaxies. Our group have investigated
the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near
infrared, optical and HI data available for a sample of these peculiar
objects. The total K-band luminosity, which mainly comes from the central
host galaxy, and the measured HI linewidth at 20% of the peak line flux
density, which traces the potential in the polar plane, place most polar
rings of the sample far from the Tully-Fisher relation defined for spiral
galaxies, with many PRGs showing larger HI linewidths than expected
for the observed K band luminosity.
This result is confirmed by a larger sample of objects, based on B-band
This observational evidence may be related to the dark halo shape and
orientation in these systems, which we study by numerical
modeling of PRG formation and dynamics: the larger rotation velocities
observed in PRGs can be explained by a flattened polar halo, aligned
with the polar ring.