No way ou tau: Epoch of Reionization Observations Do not Support Large Values of the Optical Depth to Reionization

arXiv:2607.26373 · astro-ph.CO · Submitted 2026-07-29 · Read on arXiv

Paulo Montero-Camacho, Yi Mao

astro-ph.CO

Submitted: 2026-07-29

Comments: Comments welcome! 8 pages, 5 figures. New version replaces the LambdaT model for the main model used in Ref. [5]

Code: https://github.com/paulomontero/class_gomp

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Degeneracy — 5× in this paper · explained in 3 episodes
• Cosmic Microwave Background — 4× in this paper
• Benchmark — 2× in this paper · explained in 2 episodes
• Consistency — 2× in this paper · explained in 3 episodes
• Adam — 1× in this paper · explained in 2 episodes
• Anisotropy — 1× in this paper · explained in 3 episodes
• Bispectrum — 1× in this paper · explained in 3 episodes
• Quintessence — 1× in this paper · explained in 2 episodes
• Robustness — 1× in this paper · explained in 5 episodes
• Self-consistency — 1× in this paper · explained in 2 episodes

Sources

• Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument
• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• Cosmological constraints from a joint DESI DR1 Full-Shape and DR2 BAO
• Cosmological constraints from the DESI DR1 Bispectrum Full-Shape and DR2 BAO
• Dispu$\tau$able: the high cost of a low optical depth
• Turning a negative neutrino mass into a positive optical depth
• Cosmic $\tau$ensions Indirectly Correlate with Reionization Optical Depth
• Rapid late-time reionization: constraints and cosmological implications
• A New Constraint on the Optical Depth from the Reionization History Independent of CMB Large-Scale E-Mode Polarization
• Uniting the Observed Dynamical Dark Energy Preference with the Discrepancies in $\Omega_m$ and $H_0$ Across Cosmological Probes
• Reionization and the Hubble Constant: Correlations in the Cosmic Microwave Background
• Planck 2018 results. V. CMB power spectra and likelihoods
• Reionization optical depth determination from Planck HFI data with ten percent accuracy
• The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and $\Lambda$CDM Parameters
• Updated Cosmological Constraints in Extended Parameter Space with Planck PR4, DESI Baryon Acoustic Oscillations, and Supernovae: Dynamical Dark Energy, Neutrino Masses, Lensing Anomaly, and the Hubble Tension
• Cosmology in Extended Parameter Space with DESI Data Release 2 Baryon Acoustic Oscillations: A 2$\sigma$+ Detection of Nonzero Neutrino Masses with an Update on Dynamical Dark Energy and Lensing Anomaly
• Cosmological constraints on nonphantom dynamical dark energy with DESI Data Release 2 Baryon Acoustic Oscillations: A 3$\sigma$+ lensing anomaly
• Into the Gompverse: A robust Gompertzian reionization model for CMB analyses
• Raising the reionization optical depth with inflationary CMB features
• Updated Constraints on Infrared Cutoff Models and Implications for Large-Scale CMB Anomalies

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