Imaging the Active Galactic Nucleus Torus in Cygnus A

We present the first direct imaging of what may be the thick torus in the active galactic nucleus (AGN) of the archetype powerful radio galaxy Cygnus A, using the Jansky Very Large Array at 18–48 GHz, with a resolution down to 45 mas. Such a torus has long been a key component of AGN models, but direct imaging on the relevant physical scales in sources of extreme (quasar-like) luminosities, remains scarce. An elongated structure, perpendicular to the radio jets and centered on the core, is well resolved, with a full length of 0farcs48 (528 pc), and a full width of 0farcs26 (286 pc). The radio emission spectrum is consistent with optically thin free–free emission. We present a toy model of a flaring torus, with a half-opening angle for the poloidal region of 62°. The radio jets are oriented along the poles. The observations require a clumpy gas distribution, with the free–free emission dominated by clumps with densities ≥4000 cm−3.