The impact of very massive stars on the chemical evolution of extremely
  metal-poor galaxies
  In recent observations of extremely metal-poor low-mass starburst galaxies,
almost solar Fe/O ratios are reported, despite N/O ratios consistent with the
low metallicity. We investigate if the peculiar Fe/O ratios can be a
distinctive signature of an early enrichment produced by very massive objects
dying as Pair-Instability Supernovae (PISN). We run chemical evolution models
with yields that account for the contribution by PISN. We use both the recent
non-rotating stellar yields from Goswami et al. 2021, and new yields from
rotating very massive stars calculated on purpose in this work. We also search
for the best initial mass function (IMF) that is able to reproduce the
observations. We can reproduce the observations by adopting a bi-modal IMF and
by including an initial burst of rotating very massive stars. Only with a burst
of very massive stars can we reproduce the almost solar Fe/O ratios at the
estimated young ages. We also confirm that rotation is absolutely needed to
concomitantly reproduce the observed N/O ratios. These results stress the
importance of very massive stars in galactic chemical evolution studies and
strongly support a top-heavy initial mass function in the very early
evolutionary stages of metal poor starburst galaxies.
