A Pop III.1-driven early ionization phase at z=20 yields τ=0.087 consistent with pkSZ and Lyα constraints, potentially resolving BAO-CMB tensions on neutrino mass.
The Impact of Population III.1 Flash Reionization for CMB Polarization and Thomson Scattering Optical Depth
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abstract
The Population III.1 theory for supermassive black hole (SMBH) formation predicts a very early ($z\sim20-25$) 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 $z\sim 10$. The overall Thomson scattering optical depth, $\tau$, from the Pop III.1 Flash has been shown to be $\tau_{\rm PopIII.1}\sim0.03$, leading to a total $\tau\sim0.08-0.09$. 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 $\Lambda$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 $l\lesssim\:$6 modes is dramatically reduced compared to usual low-$z$ reionization models for the same value of $\tau$, while the power at $l\gtrsim\:$6 is boosted. Thus the Pop III.1 reionization scenario provides a natural way to increase $\tau$, while remaining closer to the latest CMB low-$l$ polarization observations.
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UNVERDICTED 2representative citing papers
Marginalizing over generalized slow-roll inflationary templates for the CMB low-power feature raises the 95% upper limit on τ to 0.075 (Planck) or 0.082 (all CMB+BAO), resolving incompatibility with lower bounds.
citing papers explorer
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Fireworks at Cosmic Dawn: relieving BAO-CMB tensions with the Pop III.1 Flash
A Pop III.1-driven early ionization phase at z=20 yields τ=0.087 consistent with pkSZ and Lyα constraints, potentially resolving BAO-CMB tensions on neutrino mass.
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Raising the reionization optical depth with inflationary CMB features
Marginalizing over generalized slow-roll inflationary templates for the CMB low-power feature raises the 95% upper limit on τ to 0.075 (Planck) or 0.082 (all CMB+BAO), resolving incompatibility with lower bounds.