Polar Ring Galaxies and the Tully-Fisher relation: implications for the dark halo shape

Abstract

We have investigated the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near infrared, optical and H i 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 H i 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 -2 -many PRGs showing larger H i linewidths than expected for the observed K band luminosity. This result is confirmed by a larger sample of objects, based on Bband data. 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.

On the nature of the apparent ring galaxy SDSS J075234.33+292049.8

“…Note that we adopted v max = 305 km s −1 for this comparison. We also compared with the similar properties of PRGs in the right panels of figs 1 and 2 of Arnaboldi et al (2004), adopting Δ v 20 = 610 km s −1 . RG1 lies on the right dashed line in their fig.…”

“…Note that we adopted vmax=305 km s −1 for this comparison. We also compared with the similar properties of PRGs in the right panels of Figures 1 and 2 of Arnaboldi et al (2004), adopting ∆v20=610 km s −1 . RG1 lies on the right dashed line in their Figure 1, near the top of distribution, considerably to the right of the spiral galaxies line plotted in their Figure 2, and on the same line as the S0 galaxies.…”