Dynamical Constraints on the Origin of Multiple Stellar Populations in
  Globular Clusters
  We have carried out a large grid of N-body simulations in order to
investigate if mass-loss as a result of primordial gas expulsion can be
responsible for the large fraction of second generation stars in globular
clusters (GCs) with multiple stellar populations (MSPs). Our clusters start
with two stellar populations in which $10\%$ of all stars are second generation
stars. We simulate clusters with different initial masses, different ratios of
the half-mass radius of first to second generation stars, different primordial
gas fractions and Galactic tidal fields with varying strength. We then let our
clusters undergo primordial gas-loss and obtain their final properties such as
mass, half-mass radius and the fraction of second generation stars. Using our
N-body grid we then perform a Monte Carlo analysis to constrain the initial
masses, radii and required gas expulsion time-scales of GCs with MSPs. Our
results can explain the present-day properties of GCs only if (1) a substantial
amount of gas was present in the clusters after the formation of second
generation stars and (2) gas expulsion time-scales were extremely short
($\lesssim 10^5$ yr). Such short gas expulsion time-scales are in agreement
with recent predictions that dark remnants have ejected the primordial gas from
globular clusters, and pose a potential problem for the AGB scenario. In
addition, our results predict a strong anti-correlation between the number
ratio of second-generation stars in GCs and the present-day mass of GCs. So
far, the observational data show only a significantly weaker anti-correlation,
if any at all.
