The nuclear dust lane of Circinus: collimation without a torus
  In some AGN, nuclear dust lanes connected to kpc-scale dust structures
provide all the extinction required to obscure the nucleus, challenging the
role of the dusty torus proposed by the Unified Model. In this letter we show
the pc-scale dust and ionized gas maps of Circinus constructed using
sub-arcsec-accuracy registration of infrared VLT AO images with optical
\textit{Hubble Space Telescope} images. We find that the collimation of the
ionized gas does not require a torus but is caused by the distribution of dust
lanes of the host galaxy on $\sim$10 pc scales. This finding questions the
presumed torus morphology and its role at parsec scales, as one of its main
attributes is to collimate the nuclear radiation, and is in line with
interferometric observations which show that most of the pc-scale dust is in
the polar direction. We estimate that the nuclear dust lane in Circinus
provides $1/3$ of the extinction required to obscure the nucleus. This
constitutes a conservative lower limit to the obscuration at the central
parsecs, where the dust filaments might get optically thicker if they are the
channels that transport material from $\sim$100 pc scales to the centre.
