On the accretion wake model of radio jets of galaxies

The possibility is investigated as to whether jet streams associated with a galaxy or a quasar are explicable as accretion wakes which form when a gravitating body moves through an intergalactic medium with supersonic speed. A comparison of the theory based upon column accretion with a recently observed radio jet of NGC6251 gives good agreement regarding the geometrical shape of the jet and energy stored therein, provided the relative motion has a large Mach number and intergalactic density --2 x 10-28/gcm-3 is assumed. Again, the observed nuclear jet of NGC6251 may be explicable along these lines. An accretion hypothesis is specific enough to relate the density and magnetic field in the jet to those of intergalactic gas. Galactic radio jets observed so far are one sided. As for any model which ascribes jets to an outburst of relativistic particles emerging in two opposite directions from a galactic nucleus, it remains to explain the above observed result. (author)