Formation and fate of low metallicity stars in IllustrisTNG50
  Low metallicity stars give rise to unique spectacular transients and are of
immense interest for understanding stellar evolution. Their importance has only
grown further with the recent detections of mergers of stellar mass black holes
that likely originate mainly from low metallicity progenitor systems. Moreover,
the formation of low metallicity stars is intricately linked to galaxy
evolution, in particular to early enrichment and to later accretion and mixing
of lower metallicity gas. Because low metallicity stars are difficult to
observe directly, cosmological simulations are crucial for understanding their
formation. Here we quantify the rates and locations of low metallicity star
formation using the high-resolution TNG50 magnetohydrodynamical cosmological
simulation, and we examine where low metallicity stars end up at $z=0$. We find
that $20\%$ of stars with $Z_*<0.1\,\mathrm{Z_\odot}$ form after $z=2$, and
that such stars are still forming in galaxies of all masses at $z=0$ today.
Moreover, most low-metallicity stars at $z=0$ reside in massive galaxies. We
analyse the radial distribution of low metallicity star formation, and discuss
the curious case of seven galaxies in TNG50 that form stars from primordial gas
even at $z=0$.
