Globular Cluster formation in a collapsing supershell
  Primordial clouds are supposed to host the so-called population III stars.
These stars are very massive and completely metal-free. The final stage of the
life of population III stars with masses between 130 and 260 solar masses is a
very energetic hypernova explosion. A hypernova drives a shock, behind which a
spherically symmetric very dense supershell forms, which might become
gravitationally unstable, fragment, and form stars. In this paper we study
under what conditions can an expanding supershell become gravitationally
unstable and how the feedback of these supershell stars (SSSs) affects its
surroundings. We simulate, by means of a 1-D Eulerian hydrocode, the early
evolution of the primordial cloud after the hypernova explosion, the formation
of SSSs, and the following evolution, once the SSSs start to release energy and
heavy elements into the interstellar medium. Our results indicate that a shell,
enriched with nucleosynthetic products from SSSs, propagates inwards, towards
the center of the primordial cloud. In a time span of a few Myr, this
inward-propagating shell reaches a distance of only a few parsec away from the
center of the primordial cloud. Its density is extremely high and its
temperature very low, thus the conditions for a new episode of star formation
are achieved. We study what fraction of these two distinct populations of stars
can remain bound and survive until the present day. We study also under what
conditions can this process repeat and form multiple stellar populations. We
extensively discuss whether the proposed scenario can help to explain some open
questions of the formation mechanism of globular clusters.
