Evolution of two stellar populations in globular clusters II. Effects of
  primordial gas expulsion
  We investigate the early evolution of two distinct populations of low-mass
stars in globular clusters under the influence of primordial gas expulsion
driven by supernovae to study if this process can increase the fraction of
second generation stars at the level required by observations. We analyse
N-body models that take into account the effect of primordial gas expulsion. We
divide the stars into two populations which mimic the chemical and dynamical
properties of stars in globular clusters so that second generation stars start
with a more centrally concentrated distribution. The main effect of gas
expulsion is to eject preferentially first generation stars while second
generation stars remain bound to the cluster. In the most favourable cases
second generation stars can account for 60% of the bound stars we see today. We
also find that at the end of the gas expulsion phase, the radial distribution
of the two populations is still different, so that long-term evolution will
further increase the fraction of second generation stars. The large fraction of
chemically anomalous stars is readily explainable as a second generation of
stars formed out of the slow winds of rapidly rotating massive stars if
globular clusters suffer explosive residual gas expulsion for a star formation
efficiency of about 0.33.
