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.