2002/07/03 by U. Bach, T. P. Krichbaum, Bach, U. +7
Engineering · Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Particle accelerators and beam dynamics #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0207082
4 pages, 6 figures, appears in: Proceedings of the 6th European VLBI Network Symposium held on June 25th-28th in Bonn, Germany. Edited by: E. Ros, R.W. Porcas, A.P. Lobanov, and J.A. Zensus
arxiv created 2002/07/03 · openalex publication_date 2002/07/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Our recent VLBI observations of the prominent FR II radio galaxy Cygnus A with the EVN and the VLBA reveal a pronounced two-sided jet structure. At 5 GHz, we now have 4 epochs from 1986, 1991 (Carilli et al., 1991 & 1994), 1996 and 2002 from which we could derive the kinematics of the jet and counter-jet. On the jet side and on mas scales, the jet seems to accelerate from β\rm app≈ 0.1-0.2 (Krichbaum et al. 1998) at core-separations near 1 mas to β\rm app≈ 0.4-0.6 at r ≥ 4 mas (H0=100 km s-1 Mpc-1, q0=0.5). For the first time we also measure significant structural variability on the counter-jet side. For this, we derive a motion of β\rm app=0.35±0.2 at r=9.5 mas. The flat spectrum of the inner region of the counter-jet (free-free absorption) and the frequency dependence of the jet to counter-jet ratio support strong evidence for an obscuring torus in front of the counter-jet (Bach et al. in prep, Krichbaum et al. 1998).