Flash Ionization of the Early Universe by Pop III.1 Supermassive Stars

Fuente: arXiv
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Autor principal: Tan, Jonathan C.
Formato: Preprint
Publicado: 2025
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author Tan, Jonathan C.
author_facet Tan, Jonathan C.
contents The Pop III.1 theory for supermassive black hole (SMBH) formation predicts that a substantial fraction of the early universe was ionized by supermassive stars at redshifts $z\sim20-30$, an era we refer to as ``The Flash''. This is followed by recombination to a mainly neutral state within a few tens of Myr. Here we discuss the implication of this ionization for the scattering optical depth of the cosmic microwave background (CMB), $τ$. We find a fiducial contribution of $τ_{\rm PopIII.1}\sim0.04$. Combining this with the contribution to reionization by standard galaxy populations at $z\lesssim 10$ with $τ_{\rm gal}\simeq0.06$, yields a total of $τ\simeq0.10$. As noted recently by several authors, such a value may help resolve apparent ``problems'' faced by $Λ$CDM of discrepant CMB-based measures of the Hubble constant (``Hubble tension''), as well as negative neutrino masses and dynamical dark energy that have been implied by recent Baryonic Acoustic Oscillation (BAO) results from the Dark Energy Spectroscopic Instrument (DESI). In addition, free-free emission from The Flash boosts the cosmic radio background, which could help explain the large 21-cm absorption depth reported by the Experiment to Detect the Global EoR Signature (EDGES).
format Preprint
id arxiv_https___arxiv_org_abs_2506_18490
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Flash Ionization of the Early Universe by Pop III.1 Supermassive Stars
Tan, Jonathan C.
Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
The Pop III.1 theory for supermassive black hole (SMBH) formation predicts that a substantial fraction of the early universe was ionized by supermassive stars at redshifts $z\sim20-30$, an era we refer to as ``The Flash''. This is followed by recombination to a mainly neutral state within a few tens of Myr. Here we discuss the implication of this ionization for the scattering optical depth of the cosmic microwave background (CMB), $τ$. We find a fiducial contribution of $τ_{\rm PopIII.1}\sim0.04$. Combining this with the contribution to reionization by standard galaxy populations at $z\lesssim 10$ with $τ_{\rm gal}\simeq0.06$, yields a total of $τ\simeq0.10$. As noted recently by several authors, such a value may help resolve apparent ``problems'' faced by $Λ$CDM of discrepant CMB-based measures of the Hubble constant (``Hubble tension''), as well as negative neutrino masses and dynamical dark energy that have been implied by recent Baryonic Acoustic Oscillation (BAO) results from the Dark Energy Spectroscopic Instrument (DESI). In addition, free-free emission from The Flash boosts the cosmic radio background, which could help explain the large 21-cm absorption depth reported by the Experiment to Detect the Global EoR Signature (EDGES).
title Flash Ionization of the Early Universe by Pop III.1 Supermassive Stars
topic Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2506.18490