Kavli Affiliate: Eiichiro Komatsu
| Summary:
The Population III.1 theory for supermassive black hole (SMBH) formation predicts a very early ($zsim20-25$) transient phase, the “Pop III.1 Flash”, of cosmic reionization powered by supermassive stars that are SMBH progenitors. The universe then quickly recombined to become mostly neutral, with this state persisting until galaxies begin to reionize intergalactic gas again at $zsim 10$. The overall Thomson scattering optical depth, $τ$, from the Pop III.1 Flash has been shown to be $τ_rm PopIII.1sim0.03$, leading to a total $τsim0.08-0.09$. Such a value, while significantly larger than that previously inferred from it Planck observations of the low-$l$ $EE$ polarization power spectrum of the CMB, can help relieve several “tensions” faced by the standard $Λ$CDM cosmological model, especially the preference for negative neutrino masses and dynamic dark energy. Here we compute $EE$ power spectra of example models of the Pop III.1 Flash. We find that, because of its very high redshift, the contribution to $llesssim:$6 modes is dramatically reduced compared to usual low-$z$ reionization models for the same value of $τ$, while the power at $lgtrsim:$6 is boosted. Thus the Pop III.1 reionization scenario provides a natural way to increase $τ$, while remaining closer to the latest CMB low-$l$ polarization observations.
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