Radiation pattern and outflow geometry: a new probe of black hole spin?
  We explore the impact of the central black hole (BH) spin on the large-scale
properties of the host galaxy, by considering radiative feedback. The BH spin
determines the radiation pattern from the accretion disc, which directly
imprints on the geometry of the radiation-driven outflows. We show that for low
BH spins, the emission is vertically focused, giving rise to polar/prolate
outflows; while for high BH spins, the radiation pattern is more isotropic,
leading to quasi-spherical/oblate outflows. Reversing the argument, we can
potentially deduce the spin of the central BH from the observed morphology of
galactic outflows. In principle, this may provide a novel way of constraining
the central BH spin from galaxy-scale observations. Indeed, the BH spin can
have significant macroscopic effects on galactic scales, ultimately shaping the
large-scale feedback and the resulting obscuration.
