MegaMorph -- multi-wavelength measurement of galaxy structure:
  physically meaningful bulge-disc decomposition of galaxies near and far
  Bulge-disc decomposition is a valuable tool for understanding galaxies.
However, achieving robust measurements of component properties is difficult,
even with high quality imaging, and it becomes even more so with the imaging
typical of large surveys.
  In this paper we consider the advantages of a new, multi-band approach to
galaxy fitting. We perform automated bulge-disc decompositions for 163 nearby
galaxies, by simultaneously fitting multiple images taken in five photometric
filters. We show that we are able to recover structural measurements that agree
well with various other works, and confirm a number of key results. We
additionally use our results to illustrate the link between total S\'ersic
index and bulge-disc structure, and demonstrate that the visually
classification of lenticular galaxies is strongly dependent on the inclination
of their disc component.
  By simulating the same set of galaxies as they would appear if observed at a
range of redshifts, we are able to study the behaviour of bulge-disc
decompositions as data quality diminishes. We examine how our multi-band fits
perform, and compare to the results of more conventional, single-band methods.
Multi-band fitting improves the measurement of all parameters, but particularly
the bulge-to total flux ratio and component colours. We therefore encourage the
use of this approach with future surveys.
