Orientation of the cores of hybrid morphology radio sources
  The FRI/FRII dichotomy is a much debated issue in the astrophysics of
extragalactic radio sources. Study of the properties of HYbrid MOrphology Radio
Sources (HYMORS) may bring crucial information and lead to a step forward in
understanding the origin of FRI/FRII dichotomy. HYMORS are a rare class of
double-lobed radio sources where each of the two lobes clearly exhibits a
different FR morphology. This article describes follow-up high resolution VLBA
observations of the five discovered by us HYMORS. The main aim of the
observations was to answer the questions of whether the unusual radio
morphology is connected to the orientation of objects towards the observer. We
obtained the high resolution radio maps of five hybrid radio morphology objects
with the VLBA at C-band and L-band. Two of them revealed milliarcsecond
core-jet structures, the next two objects showed hints of parsec-scale jets,
and the last one remained point-like at both frequencies. We compared
properties of observed milliarcsecond structures of hybrid sources with the
larger scale ones previously detected with the VLA. We find that on both scales
the fluxes of their central components are similar, which may indicate the lack
of additional emission in the proximity of the nucleus. This suggests that jets
present on the 1-10 kpc scale in those objects are FRII-like. When possible,
the detected core-jet structures were used for estimating the core's spatial
orientation. The result is that neither the FRI-like nor the FRII-like side is
preferred, which may suggest that no specific spatial orientation of HYMORS is
required to explain their radio morphology. Their estimated viewing angles
indicate they are unbeamed objects. The 178 MHz luminosity of observed HYMORS
exceed the traditional FRI/FRII break luminosity, indicating they have radio
powers similar to FRIIs.
