Compact radio emission from z~0.2 X-ray bright AGN
  Radio and X-ray emission of AGN appears to be correlated. The details of the
underlying physical processes, however, are still not fully understood, i.e.,
to what extent is the X-ray and radio emission originating from the same
relativistic particles or from the accretion-disk or corona or both. We study
the cm radio emission of an SDSS/ROSAT/FIRST matched sample of 13 X-raying AGN
in the redshift range 0.11< z < 0.37 at high angular resolution with the goal
of searching for jet structures or diffuse, extended emission on sub-kpc
scales. We use MERLIN at 18 cm for all objects and Western EVN at 18 cm for
four objects to study the radio emission on scales of ~500 pc and ~40 pc for
the MERLIN and EVN observations, respectively. The detected emission is
dominated by compact nuclear radio structures. We find no kpc collimated jet
structures. The EVN data indicate for compact nuclei on 40 pc scales, with
brightness temperatures typical for accretion-disk scenarios. Comparison with
FIRST shows that the 18 cm emission is resolved out up to 50% by MERLIN.
Star-formation rates based on large aperture SDSS spectra are generally too
small to produce considerable contamination of the nuclear radio emission. We
can, therefore, assume the 18 cm flux densities to be produced in the nuclei of
the AGN. Together with the ROSAT soft X-ray luminosities and black hole mass
estimates from the literature, our sample objects follow closely the Merloni et
al. (2003) fundamental plane relation, which appears to trace the accretion
processes. Detailed X-ray spectral modeling from deeper hard X-ray observations
and higher angular resolution at radio wavelengths are required to further
proceed in the disentangling of jet and accretion related processes.
