The Orientation of Jets Relative to Dust Disks in Radio Galaxies

Abstract

We use Hubble Space Telescope broadband images and VLA and VLBI continuum data to study the three-dimensional orientation of jets relative to nuclear dust disks in 20 radio galaxies. The comparison between the position angles of the jets and those of the dust disk major axes shows a wide distribution, suggesting that they are not aligned preferentially perpendicular to each other. We use a statistical technique to determine the three-dimensional distribution of angles between jets and dust disk rotation axes. This analysis shows that the observations are consistent with jets homogeneously distributed over a large region, extending over polar caps of 55°-77° but seeming to avoid lying close to the plane of the dust disks. We argue that the lack of close alignment between jets and dust disks axes is not likely to be caused by feeding the nucleus with gas from mergers originated from random directions. We suggest that the misalignment can be due to a warping mechanism in the accretion disk, such as self-irradiation instability or the Bardeen-Petterson effect, or that the gravitational potential in the inner regions of the galaxy is misaligned with respect to that of the dust disk. Based partly on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.