Circumnuclear Structures in Megamaser Host Galaxies
  Using HST, we identify circumnuclear ($100$-$500$ pc scale) structures in
nine new H$_2$O megamaser host galaxies to understand the flow of matter from
kpc-scale galactic structures down to the supermassive black holes (SMBHs) at
galactic centers. We double the sample analyzed in a similar way by Greene et
al. (2013) and consider the properties of the combined sample of 18 sources. We
find that disk-like structure is virtually ubiquitous when we can resolve
$<200$ pc scales, in support of the notion that non-axisymmetries on these
scales are a necessary condition for SMBH fueling. We perform an analysis of
the orientation of our identified nuclear regions and compare it with the
orientation of megamaser disks and the kpc-scale disks of the hosts. We find
marginal evidence that the disk-like nuclear structures show increasing
misalignment from the kpc-scale host galaxy disk as the scale of the structure
decreases. In turn, we find that the orientation of both the $\sim100$ pc scale
nuclear structures and their host galaxy large-scale disks is consistent with
random with respect to the orientation of their respective megamaser disks.
