Constraints on the gamma-ray emitting region in blazars from
  multi-frequency VLBI measurements
  Single-zone synchrotron self-Compton and external Compton models are widely
used to explain broad-band Spectral Energy Distributions (SEDs) of blazars from
infrared to gamma-rays. These models bear obvious similarities to the
homogeneous synchrotron cloud model which is often applied to explain radio
emission from individual components of parsec-scale radio jets. The
parsec-scale core, typically the brightest and most compact feature of blazar
radio jet, could be the source of high-energy emission. We report on ongoing
work to test this hypothesis by deriving the physical properties of
parsec-scale radio emitting regions of twenty bright Fermi blazars using
dedicated 5-43 GHz VLBA observations and comparing these parameters to results
of SED modeling.
