A new strategy for matching observed and simulated lensing galaxies
  The study of strong-lensing systems conventionally involves constructing a
mass distribution that can reproduce the observed multiply-imaging properties.
Such mass reconstructions are generically non-unique. Here, we present an
alternative strategy: instead of modelling the mass distribution, we search
cosmological galaxy-formation simulations for plausible matches. In this paper
we test the idea on seven well-studied lenses from the SLACS survey. For each
of these, we first pre-select a few hundred galaxies from the EAGLE
simulations, using the expected Einstein radius as an initial criterion. Then,
for each of these pre-selected galaxies, we fit for the source light
distribution, while using MCMC for the placement and orientation of the lensing
galaxy, so as to reproduce the multiple images and arcs. The results indicate
that the strategy is feasible, and even yields relative posterior probabilities
of two different galaxy-formation scenarios, though these are not statistically
significant yet. Extensions to other observables, such as kinematics and
colours of the stellar population in the lensing galaxy, is straightforward in
principle, though we have not attempted it yet. Scaling to arbitrarily large
numbers of lenses also appears feasible. This will be especially relevant for
upcoming wide-field surveys, through which the number of galaxy lenses will
rise possibly a hundredfold, which will overwhelm conventional modelling
methods.
