High-redshift obscured quasars: radio emission at sub-kiloparsec scales
  The radio properties of 11 obscured `radio-intermediate' quasars at redshifts
z>~2 have been investigated using the European
Very-Long-Baseline-Interferometry Network (EVN) at 1.66 GHz. A sensitivity of
~25 micro Jy per 14x17 mas2 beam was achieved, and in 7 out of 11 sources
unresolved radio emission was securely detected. The detected radio emission of
each source accounts for ~30-100 % of the total source flux density. The
physical extent of this emission is ~<150 pc, and the derived properties
indicate that this emission originates from an active galactic nucleus (AGN).
The missing flux density is difficult to account for by star-formation alone,
so radio components associated with jets of physical size >~150 pc, and ~< 40
kpc are likely to be present in most of the sources. Amongst the observed
sample steep, flat, gigahertz-peaked and compact-steep spectrum sources are all
present. Hence, as well as extended and compact jets, examples of beamed jets
are also inferred, suggesting that in these sources, the obscuration must be
due to dust in the host galaxy, rather than the torus invoked by the unified
schemes. Comparing the total to core (~< 150 pc) radio luminosities of this
sample with different types of AGN suggests that this sample of z >~2
radio-intermediate obscured quasars shows radio properties that are more
similar to those of the high-radio-luminosity end of the low-redshift
radio-quiet quasar population than those of FR I radio galaxies. This
conclusion may reflect intrinsic differences, but could be strongly influenced
by the increasing effect of inverse-Compton cooling of extended radio jets at
high redshift.
