No evidence for missing covariance in the Pantheon+ SuperNova sample distance moduli

Bohdan Bidenko; Léon V. E. Koopmans; P. Daniel Meerburg

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arXiv · 2308.05157

No evidence for missing covariance in the Pantheon+ SuperNova sample distance moduli

Bohdan Bidenko·Léon V. E. Koopmans·P. Daniel Meerburg

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Abstract

Inspired by the discussion in the community on possible hidden systematic errors in late universe cosmological probes and non-trivial physical models developed to reduce the Hubble tension, we investigate the Pantheon and Pantheon+ SNe samples for possible deviations from the original $Λ$CDM analysis. To simultaneously account for possible systematics or deviations from $Λ$CDM, we adopt Gaussian processes to model additional covariance while making no further assumptions on their origin. We explore both stationary and non-stationarity corrections to the covariance. While small changes in the inferred cosmological parameters $H_0$ and $Ω_{m}$ can occur, we find no statistically significant evidence for missing covariance. We find an upper limit for the Gaussian processes amplitude $σ< 0.031$ mag with $95\%$ confidence, which corresponds to $20\%$ of the average statistical error in the Pantheon+ sample. The strongest effect we find on the inferred cosmological parameter posterior can reduce the statistical significance of the Hubble tension between Pantheon+ and Planck estimates from 5.3$σ$ to 4.5$σ$. Therefore, we conclude that the SN cosmological parameter inference is robust against the analysis modifications studied in this work.

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Bohdan Bidenko, Léon V. E. Koopmans, P. Daniel Meerburg. 2023-08-09. No evidence for missing covariance in the Pantheon+ SuperNova sample distance moduli. https://arxiv.org/abs/2308.05157

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