Deep, wide-field, global VLBI observations of the Hubble Deep Field
  North and Flanking Fields
  Dust is commonly present in weakly radio emitting star-forming galaxies and
this dust may obscure the signatures of accreting black holes in these objects.
We aim to uncover weak active galactic nuclei, AGN, in the faint radio source
population by means of deep high-resolution radio observations. VLBI
observations with a world-wide array at unparallelled sensitivity are carried
out to assess the nature of the faint radio source population in the Hubble
Deep Field North and its flanking fields. Images of twelve compact, AGN-driven
radio sources are presented. These represent roughly one quarter of the
detectable faint radio source sample. Most, but not all of these low power AGN
have X-ray detections. The majority of the faint radio source population must
be star-forming galaxies. Faint AGN occur in a variety of (distant) host
galaxies, and these are often accompanied by a dust-obscured starburst. Deep,
high-resolution VLBI is a unique, powerful technique to assess the occurrence
of faint AGN.
