The non-causal origin of the black hole-galaxy scaling relations
  We show that the black hole-bulge mass scaling relations observed from the
local to the high-z Universe can be largely or even entirely explained by a
non-causal origin, i.e. they do not imply the need for any physically coupled
growth of black hole and bulge mass, for example through feedback by active
galactic nuclei (AGN). Provided some physics for the absolute normalisation,
the creation of the scaling relations can be fully explained by the
hierarchical assembly of black hole and stellar mass through galaxy merging,
from an initially uncorrelated distribution of BH and stellar masses in the
early Universe. We show this with a suite of dark matter halo merger trees for
which we make assumptions about (uncorrelated) black hole and stellar mass
values at early cosmic times. We then follow the halos in the presence of
global star formation and black hole accretion recipes that (i) work without
any coupling of the two properties per individual galaxy and (ii) correctly
reproduce the observed star formation and black hole accretion rate density in
the Universe. With disk-to-bulge conversion in mergers included, our
simulations even create the observed slope of ~1.1 for the
M_BH-M_bulge-relations at z=0. This also implies that AGN feedback is not a
required (though still a possible) ingredient in galaxy evolution. In light of
this, other mechanisms that can be invoked to truncate star formation in
massive galaxies are equally justified.
