A new model for the multiple stellar populations within Terzan 5
  Recent observational studies have demonstrated that the complex stellar
system Terzan 5 (Ter 5) harbours multiple populations of stars. Several models
have attempted to interpret the large age difference of several Gyrs between
the dominant populations, but none have been universally accepted. We propose a
new scenario whereby a collision between a metal-poor Ter 5 and a giant
molecular cloud (GMC) serves as a catalyst for the generation of a super-solar
population of stars. Using numerical simulations of this new "GC-GMC" collision
scenario we demonstrate that, within a time frame of several Gyrs, our
synthetic Ter 5 was capable of interacting with a metal-rich GMC in the central
region of the Galaxy. As a consequence of this, our simulated globular cluster
(GC) is able to capture enough gas from the colliding GMC to form a new
population of metal-rich stars. Furthermore, the younger population created
from the high-density regions of the captured gas is shown to have a stronger
central mass concentration than the older metal-poor one, which is consistent
with observations. A chemical link between Ter 5 and the bulge population of
the Milky Way has long been observed and these simulations finally provide
evidence for their similarities. Our model rationalises the 5 Gyrs of
quiescence observed between the two dominant populations of Ter 5 and justifies
the existence of the young generation. We discuss the advantages and
disadvantages of the new scenario in the context of the observed physical
properties of Ter 5.
