The central pc-scale region in blazars: insights from multi-band
  observations
  The empirical relations in the black hole-accretion disk-relativistic jet
system and physical processes behind these relations are still poorly
understood, partly because they operate close to the black hole within the
central light year. Very long baseline array (VLBA) provides unparalleled
resolution at 15 GHz with which to observe the jet components at
sub-milliarcsecond scales, corresponding to sub-pc-scales for local blazars. We
discuss the jet inner structure of blazars, location and radiation mechanisms
operating in the innermost parsec-scale region of blazars, and evidence for
jet-excited broad-line region (BLR) ouflowing downstream the jet. Outflowing
BLR can provide necessary conditions for production of high energy emission
along the jet between the base of the jet and the BLR and far beyond the BLR as
evidenced by recent observations. Flat spectrum quasars and low synchrotron
peaked sources are the most likely objects to host the outfllowing BLR. From
the $\gamma$-ray absorption arguments, we propose that the jet-excited region
of the outflowing BLR in quasars is small and/or gas filling factor is low, and
that the orientation and opening angle of the outflowing BLR can lead to
relevant $\gamma$-ray absorption features observed in quasars.
