What shapes a galaxy? - Unraveling the role of mass, environment and
  star formation in forming galactic structure
  We investigate the dependence of galaxy structure on a variety of galactic
and environmental parameters for ~500,000 galaxies at z<0.2, taken from the
Sloan Digital Sky Survey data release 7 (SDSS-DR7). We utilise bulge-to-total
stellar mass ratio, (B/T)_*, as the primary indicator of galactic structure,
which circumvents issues of morphological dependence on waveband. We rank
galaxy and environmental parameters in terms of how predictive they are of
galaxy structure, using an artificial neural network approach. We find that
distance from the star forming main sequence (Delta_SFR), followed by stellar
mass (M_*), are the most closely connected parameters to (B/T)_*, and are
significantly more predictive of galaxy structure than global star formation
rate (SFR), or any environmental metric considered (for both central and
satellite galaxies). Additionally, we make a detailed comparison to the
Illustris hydrodynamical simulation and the LGalaxies semi-analytic model. In
both simulations, we find a significant lack of bulge-dominated galaxies at a
fixed stellar mass, compared to the SDSS. This result highlights a potentially
serious problem in contemporary models of galaxy evolution.
