Simulations of the Milky Way's central molecular zone -- II. Star
  formation
  The Milky Way's central molecular zone (CMZ) has emerged in recent years as a
unique laboratory for the study of star formation. Here we use the simulations
presented in Tress et al. 2020 to investigate star formation in the CMZ. These
simulations resolve the structure of the interstellar medium at sub-parsec
resolution while also including the large-scale flow in which the CMZ is
embedded. Our main findings are as follows. (1) While most of the star
formation happens in the CMZ ring at $R\gtrsim100 {\, \rm pc}$, a significant
amount also occurs closer to SgrA* at $R \lesssim 10{\, \rm pc}$. (2) Most of
the star formation in the CMZ happens downstream of the apocentres, consistent
with the "pearls-on-a-string" scenario, and in contrast to the notion that an
absolute evolutionary timeline of star formation is triggered by pericentre
passage. (3) Within the timescale of our simulations ($\sim100$ Myr), the
depletion time of the CMZ is constant within a factor of $\sim2$. This suggests
that variations in the star formation rate are primarily driven by variations
in the mass of the CMZ, caused for example by AGN feedback or
externally-induced changes in the bar-driven inflow rate, and not by variations
in the depletion time. (4) We study the trajectories of newly born stars in our
simulations. We find several examples that have age and 3D velocity compatible
with those of the Arches and Quintuplet clusters. Our simulations suggest that
these prominent clusters originated near the collision sites where the
bar-driven inflow accretes onto the CMZ, at symmetrical locations with respect
to the Galactic centre, and that they have already decoupled from the gas in
which they were born.
