Morphology of X-ray AGN hosts
A sizeable fraction (~30%) of X-ray selected AGN at z<1
is asociated with spiral galaxy hosts. This argues against major
mergers as the only mechanism for triggering accretion events
onto supermassive black holes.
The top figure is a gallery of the Hubble Space Telescope optical
morphologies of moderate luminosity X-ray selected at z<1. They show
diverse morphologies, inlcuding disk, bulge-dominated early-type
hosts and morphologically disturbed systems. If major galaxy mergers
are responsible for triggering black hole accretion, one expects AGN
to live in hosts with disturbed/irregular morphology or bulges,
i.e. the end product of major mergers. The fact that AGN are
observed in disk galaxies suggests that processes other than major
mergers also play a role in the growth of black holes. More details
in
Georgakakis et al. 2009.
|