3C 454.3 Reveals the Structure and Physics of Its "Blazar Zone"

Abstract

Recent multiwavelength observations of 3C 454.3, in particular during its giant outburst in 2005, put severe constraints on the location of the "blazar zone," its dissipative nature, and high-energy radiation mechanisms. As the optical, X-ray, and millimeter light curves indicate, a significant fraction of the jet energy must be released in the vicinity of the millimeter photosphere; i.e., at distances where, due to lateral expansion, the jet becomes transparent at millimeter wavelengths. We conclude that this region is located at ~10 pc, which is also the distance that coincides with the location of the hot dust region. This location is consistent with the high-amplitude variations observed on a ~10 day timescale, provided that the Lorentz factor of a jet is Γ_j ~ 20. We argue that dissipation is driven by the reconfinement shock and demonstrate that X-rays and γ-rays are likely to be produced via inverse Compton scattering of near- and mid-IR photons emitted by the hot dust. We also infer that the largest gamma-to-synchrotron luminosity ratio ever recorded in this object, which took place during its lowest luminosity states, could be simply due to weaker magnetic fields carried by a less powerful jet.