N-body models of globular clusters: metallicity, half-light radii and
  mass-to-light ratios
  Size differences of approx. 20% between red (metal-rich) and blue
(metal-poor) sub-populations of globular clusters have been observed,
generating an ongoing debate as to weather these originate from projection
effects or the difference in metallicity. We present direct N-body simulations
of metal-rich and metal-poor stellar populations evolved to study the effects
of metallicity on cluster evolution. The models start with N = 100000 stars and
include primordial binaries. We also take metallicity dependent stellar
evolution and an external tidal field into account. We find no significant
difference for the half-mass radii of those models, indicating that the
clusters are structurally similar. However, utilizing observational tools to
fit half-light (or effective) radii confirms that metallicity effects related
to stellar evolution combined with dynamical effects such as mass segregation
produce an apparent size difference of 17% on average. The metallicity effect
on the overall cluster luminosity also leads to higher mass-to-light ratios for
metal-rich clusters.
