Although we have discussed several models concerning powerful radio galaxies
and radio-loud quasars, there are still several questions about our sample
which have not been discussed. For instance, why do flux-asymmetric sources
have a magnetic field at along the jet. Is this just the result of
small number statistics or is there a fundamental proces responsible for this
effect.
Because there are, in our opinion, two separate regions where the depolarization occurs, the estimation of the electron density (using the rotation measure) isn't possible with the data we have. We don't know for instance over which pathlength we have to integrate now, because we are not sure where exactly the internal depolarization happens and by what mechanism.
We also see (again with just 6 sources) that when we have no detection of the core there is, without an exception, one lobe depolarized. A positive core detection has the result of no complete depolarization in both lobes. When using the hypothesis of just the halo as a depolarization medium this doesn't make sense. If you see no core you would expect that the source lies in the plane of the sky and therefore both lobes should have roughly the same amount of depolarization. Radio galaxies which are more turned along the line of sight should have a more luminous core (due to a small amount of relativistic beaming) and, because of the orientation of the source, one lobe depolarized (or at least much more depolarized than the other side).
These observations can be explained by the internal depolarization hypothesis. If most of the radiation comes from shock-waves within the lobe then the radiation from the jet side would have to pass the violent outher regions of the lobe to escape the galaxy. These outher regions could be responsible for the depolarization. The counter jet radiation would not have to pass through the lobes, because we might observe them at the back of the cylinder-like structure and look straight at the interaction of the shock-waves with its surrounding medium. This could be the second hint that tells us that internal depolarization is present at a substantial level.
A study of this phenomenon is needed to give more precise details. We also need
more data of high redshift radio galaxies to improve the statistics. A stack of
tapes with about 20 sources (with ) is waiting to be
processed. We might find more evidence about internal depolarization in radio
galaxies.