Modelling dust rings in early-type galaxies through a sequence of
  radiative transfer simulations and 2D image fitting
  A large fraction of early-type galaxies (ETGs) host prominent dust features,
and central dust rings are arguably the most interesting among them. We present
here `Lord Of The Rings' (LOTR), a new methodology which allows to integrate
the extinction by dust rings in a 2D fitting modelling of the surface
brightness distribution. Our pipeline acts in two steps, first using the
surface fitting software GALFIT to determine the unabsorbed stellar emission,
and then adopting the radiative transfer code SKIRT to apply dust extinction.
We apply our technique to NGC 4552 and NGC 4494, two nearby ETGs. We show that
the extinction by a dust ring can mimic, in a surface brightness profile, a
central point source (e.g. an unresolved nuclear stellar cluster or an active
galactic nucleus; AGN) superimposed to a `core' (i.e. a central flattening of
the stellar light commonly observed in massive ETGs). We discuss how properly
accounting for dust features is of paramount importance to derive correct
fluxes especially for low luminosity AGNs (LLAGNs). We suggest that the
geometries of dust features are strictly connected with how relaxed is the
gravitational potential, i.e. with the evolutionary stage of the host galaxy.
Additionally, we find hints that the dust mass contained in the ring relates to
the AGN activity.
