Proper motion in Cygnus A
نویسندگان
چکیده
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. 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 βapp ≈ 0.1 − 0.2 (Krichbaum et al. 1998) at core-separations near 1 mas to βapp ≈ 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 βapp = 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 (Krichbaum et al. 1998).
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