A dichotomy in radio jet orientations in elliptical galaxies
  We have investigated the correlations between optical and radio isophotal
position angles for 14302 SDSS galaxies with r magnitudes brighter than 18. All
the galaxies are identified with extended FIRST radio sources. For passive
early-type galaxies, which we distinguish from the others by using the colour,
concentration and their principal components, we find a strong statistical
alignment of the radio axes with the optical minor axes. Since the radio
emission is driven by accretion on to a nuclear black hole we argue that the
observed correlation gives new insight into the structure of elliptical
galaxies, for example, whether or not the nuclear kinematics are decoupled from
the rest of the galaxy. Our results imply that a significant fraction of the
galaxies are oblate spheroids, perhaps rotationally supported, with their radio
emission aligned with the stellar minor axis. Remarkably, the strength of the
correlation of the radio major axis with the optical minor axis depends on
radio loudness. Those objects with a low ratio of FIRST radio flux density to
total stellar light show a strong minor axis correlation while the stronger
radio sources do not. This split may reflect different formation histories and
we suggest this may be a new manifestation of the better known dichotomy
between slow rotating and fast rotating ellipticals.
