| Description: | Relativistic jets in AGN in general, and in blazars in particular, are among the most energetic and powerful astrophysical objects known so far. Their relativistic nature provides them the ability to emit profusely in all spectral ranges from radio wavelengths to gamma-rays, as well as abrupt variability in all time scales (from hours to years). Since the birth of gamma-ray astronomy, locating the origin of gamma-ray emission has been a fundamental problem for the knowledge of the emission processes involved. Deep and densely time sampled VLBI polarimetric monitoring programs and several other facilities at most of the available spectral ranges (including the Fermi Gamma-ray Space Telescope) are starting to shed light for the case of some blazars. After a short review of the status of the problem, some of my latest results locating the GeV emission in the jets of some blazars, at >10 parsec from the central AGN engine, will be presented together with their implications about the gamma ray emission mechanisms involved. |
