The stratified two-sided jet of Cygnus A. Acceleration and collimation

High-resolution Very-Long-Baseline Interferometry observations of relativistic jets are essential to constrain fundamental parameters of jet formation models. At a distance of 249 Mpc, Cygnus A is a unique target for such studies, being the only Fanaroff-Riley Class II radio galaxy for which a detailed sub-parsec scale imaging of the base of both jet and counter-jet can be obtained. Observing at millimeter wavelengths unveils those regions which appear self-absorbed at longer wavelengths and enables an extremely sharp view towards the nucleus to be obtained. We performed 7 mm Global VLBI observations, achieving ultra-high resolution imaging on scales down to 90 $\mu$as. This resolution corr…