Population III star explosions and Planck 2018 data
  We investigate the effect of the population III (Pop III) stars supernova
explosion~(SN) on the high redshifts reionization history using the latest
Planck data. It is predicted that massive Pop~III stars~($130M_\odot\leq M\leq
270M_\odot$) explode energetically at the end of their stellar life as
pair-instability supernovae (PISNe). In the explosion, supernova remnants grow
as hot ionized bubbles and enhance the ionization fraction in the early stage
of the reionization history. This enhancement affects the optical depth of the
cosmic microwave background~(CMB) and generates the additional anisotropy of
the CMB polarization on large scales. Therefore, analyzing the Planck
polarization data allows us to examine the Pop III star SNe and the abundance
of their progenitors, massive Pop III stars. In order to model the SN
contribution to reionization, we introduce a new parameter $\zeta$, which
relates to the abundance of the SNe to the collapse fraction of the Universe.
Using the Markov chain Monte Carlo method with the latest Planck polarization
data, we obtain the constraint on our model parameter, $\zeta$. Our constraint
tells us that observed CMB polarization is consistent with the abundance of
PISNe predicted from the star formation rate and initial mass function of Pop
III stars in recent cosmological simulations. We also suggest that combining
further observations on the late reionization history such as high redshift
quasi-stellar object~(QSO) observations can provide tighter constraints and
important information on the nature of Pop III stars.
