NuSTAR observations of water megamaser AGN
  Aims. Study the connection between the masing disk and obscuring torus in
Seyfert 2 galaxies.
  Methods. We present a uniform X-ray spectral analysis of the high energy
properties of 14 nearby megamaser Active Galactic Nuclei observed by NuSTAR. We
use a simple analytical model to localize the maser disk and understand its
connection with the torus by combining NuSTAR spectral parameters with
available physical quantities from VLBI mapping.
  Results. Most of the sources analyzed are heavily obscured, showing a column
density in excess of $\sim 10^{23}$ cm$^{-2}$. In particular, $79\%$ are
Compton-thick ($N_{\rm H} > 1.5 \times 10^{24}$ cm$^{-2}$). Using column
densities measured by NuSTAR, with the assumption that the torus is the
extension of the maser disk, and further assuming a reasonable density profile,
the torus dimensions can be predicted. They are found to be consistent with
mid-IR interferometry parsec-scale observations of Circinus and NGC 1068. In
this picture, the maser disk is intimately connected to the inner part of the
torus. It is probably made of a large number of molecular clouds connecting the
torus and the outer part of the accretion disk, giving rise to a thin disk
rotating in most cases in Keplerian or sub-Keplerian motion. This toy model
explains the established close connection between water megamaser emission and
nuclear obscuration as a geometric effect.
