Why Are AGN and Host Galaxies Misaligned?
  It is well-established observationally that the characteristic angular
momentum axis on small scales around AGN, traced by radio jets and the putative
torus, is not well-correlated with the large-scale angular momentum axis of the
host galaxy. In this paper, we show that such misalignments arise naturally in
high-resolution simulations in which we follow angular momentum transport and
inflows from galaxy to sub-pc scales near AGN, triggered either during galaxy
mergers or by instabilities in isolated disks. Sudden misalignments can
sometimes be caused by single massive clumps falling into the center slightly
off-axis, but more generally, they arise even when the gas inflows are smooth
and trace only global gravitational instabilities. When several nested,
self-gravitating modes are present, the inner ones can precess and tumble in
the potential of the outer modes. Resonant angular momentum exchange can flip
or re-align the spin of an inner mode on a short timescale, even without the
presence of massive clumps. We therefore do not expect that AGN and their host
galaxies will be preferentially aligned, nor should the relative alignment be
an indicator of the AGN fueling mechanism. We discuss implications of this
conclusion for AGN feedback and BH spin evolution. The misalignments may mean
that even BHs accreting from smooth large-scale disks will not be spun up to
maximal rotation, and so have more modest radiative efficiencies and
inefficient jet formation. Even more random orientations are possible if there
is further, un-resolved clumpiness in the gas, and more ordered accretion may
occur if the inflow is slower and not self-gravitating.
