An observational test for star formation prescriptions in cosmological
  hydrodynamical simulations
  State-of-the-art cosmological hydrodynamical simulations of galaxy formation
have reached the point at which their outcomes result in galaxies with ever
more realism. Still, the employed sub-grid models include several free
parameters such as the density threshold, $n$, to localize the star-forming
gas. In this work, we investigate the possibilities to utilize the observed
clustered nature of star formation (SF) in order to refine SF prescriptions and
constrain the density threshold parameter. To this end, we measure the
clustering strength, correlation length and power-law index of the two-point
correlation function of young ($\tau<50$ Myr) stellar particles and compare our
results to observations from the HST Legacy Extragalactic UV Survey (LEGUS).
Our simulations reveal a clear trend of larger clustering signal and power-law
index and lower correlation length as the SF threshold increases with only mild
dependence on galaxy properties such as stellar mass or specific star formation
rate. In conclusion, we find that the observed clustering of SF is inconsistent
with a low threshold for SF ($n<1$ cm$^{-3}$) and strongly favours a high value
for the density threshold of SF ($n>10$ cm$^{-3}$), as for example employed in
the NIHAO project.
