Superluminal motion in the quasar 3C 279
Abstract
VLBI maps of the quasar 3C 279 have been made at 5, 11, and 22 GHz, at several epochs between 1981 and 1985, to study the varying structure of the compact radio source. Superluminal motion is seen in two components, with apparent speed v ~ 2.2c (for a Hubble constant H_0_ = 100 km s^-1^ Mpc^-1^ and q_0_ = 0.5), only one-quarter of the expansion rate reported in the early 1970's. The structure comprises a close double in P.A. -135^deg^, seen at all three frequencies, along with steep-spectrum emission extending a few tens of parsecs (projected) and seen only at 5 GHz. The source axis points within 10^deg^ of the kiloparsec-scale jet seen by the VLA. Spectra derived from the maps show that the NE component has the highest turnover frequency, and thus probably represents the "core" of the source. By comparing the predicted inverse-Compton X-ray emission with the measured X-ray flux, we derive lower limits to the Doppler factor δ for the compact components. The core spectrum is consistent with no beaming (δ = 1), but the SW component has δ >= 2, confirming the presence of bulk relativistic motion. Thus a simple model of a jet which is mildly relativistic (Lorentz factor γ >= 2) explains both the superluminal motion and the X-ray flux.