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| Paper: |
A Dichotomy in Radio Jet Orientations in Elliptical Galaxies |
| Volume: |
427, Accretion and Ejection in AGN: a Global View |
| Page: |
365 |
| Authors: |
Browne, I. W. A.; Battye, R. A. |
| Abstract: |
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. |
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