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Comparing the DES-SN5YR and Pantheon+ SN cosmology analyses: investigation based on ‘evolving dark energy or supernovae systematics’?

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Title: Comparing the DES-SN5YR and Pantheon+ SN cosmology analyses: investigation based on ‘evolving dark energy or supernovae systematics’?
Authors: M Vincenzi, R Kessler, P Shah, J Lee, T M Davis, D Scolnic, P Armstrong, D Brout, R Camilleri, R Chen, L Galbany, C Lidman, A Möller, B Popovic, B Rose, M Sako, B O Sánchez, M Smith, M Sullivan, P Wiseman, T M C Abbott, M Aguena, S Allam, F Andrade-Oliveira, S Bocquet, D Brooks, A Carnero Rosell, J Carretero, L N da Costa, M E S Pereira, H T Diehl, P Doel, S Everett, B Flaugher, J Frieman, J García-Bellido, E Gaztanaga, D Gruen, R A Gruendl, G Gutierrez, S R Hinton, D L Hollowood, K Honscheid, D J James, K Kuehn, O Lahav, S Lee, J L Marshall, J Mena-Fernández, R Miquel, J Muir, J Myles, A Palmese, A A Plazas Malagón, A Porredon, S Samuroff, E Sanchez, D Sanchez Cid, I Sevilla-Noarbe, E Suchyta, G Tarle, C To, D L Tucker, V Vikram, A R Walker, N Weaverdyck, J Weller
Contributors: HEP, INSPIRE
Source: Monthly Notices of the Royal Astronomical Society. 541:2585-2593
Publisher Information: Oxford University Press (OUP), 2025.
Publication Year: 2025
Subject Terms: [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
Description: Recent cosmological analyses measuring distances of type Ia supernovae (SNe Ia) and baryon acoustic oscillations (BAO) have all given similar hints at time-evolving dark energy. To examine whether underestimated SN Ia systematics might be driving these results, Efstathiou (2025) compared overlapping SN events between Pantheon+ and DES-SN5YR (20 per cent SNe are in common), and reported evidence for an $\sim$0.04 mag offset between the low- and high-redshift distance measurements of this subsample of events. If this offset is arbitrarily subtracted from the entire DES-SN5YR sample, the preference for evolving dark energy is reduced. In this paper, we show that this offset is mostly due to different corrections for Malmquist bias between the two samples; therefore, an object-to-object comparison can be misleading. Malmquist bias corrections differ between the two analyses for several reasons. First, DES-SN5YR used an improved model of SN Ia luminosity scatter compared to Pantheon+ but the associated scatter-model uncertainties are included in the error budget. Secondly, improvements in host mass estimates in DES-SN5YR also affected SN standardized magnitudes and their bias corrections. Thirdly, and most importantly, the selection functions of the two compilations are significantly different, hence the inferred Malmquist bias corrections. Even if the original scatter model and host properties from Pantheon+ are used instead, the evidence for evolving dark energy from CMB, DESI BAO Year 1 and DES-SN5YR is only reduced from 3.9$\sigma$ to 3.3$\sigma$, consistent with the error budget. Finally, in this investigation, we identify an underestimated systematic uncertainty related to host galaxy property uncertainties, which could increase the final DES-SN5YR error budget by 3 per cent. In conclusion, we confirm the validity of the published DES-SN5YR results.
Document Type: Article
Language: English
ISSN: 1365-2966
0035-8711
DOI: 10.1093/mnras/staf943
Access URL: https://hal.science/hal-04902864v1
https://doi.org/10.1093/mnras/staf943
Rights: CC BY
Accession Number: edsair.doi.dedup.....cfe14fcc24004e622e97d546d34d97d0
Database: OpenAIRE
Description
Abstract:Recent cosmological analyses measuring distances of type Ia supernovae (SNe Ia) and baryon acoustic oscillations (BAO) have all given similar hints at time-evolving dark energy. To examine whether underestimated SN Ia systematics might be driving these results, Efstathiou (2025) compared overlapping SN events between Pantheon+ and DES-SN5YR (20 per cent SNe are in common), and reported evidence for an $\sim$0.04 mag offset between the low- and high-redshift distance measurements of this subsample of events. If this offset is arbitrarily subtracted from the entire DES-SN5YR sample, the preference for evolving dark energy is reduced. In this paper, we show that this offset is mostly due to different corrections for Malmquist bias between the two samples; therefore, an object-to-object comparison can be misleading. Malmquist bias corrections differ between the two analyses for several reasons. First, DES-SN5YR used an improved model of SN Ia luminosity scatter compared to Pantheon+ but the associated scatter-model uncertainties are included in the error budget. Secondly, improvements in host mass estimates in DES-SN5YR also affected SN standardized magnitudes and their bias corrections. Thirdly, and most importantly, the selection functions of the two compilations are significantly different, hence the inferred Malmquist bias corrections. Even if the original scatter model and host properties from Pantheon+ are used instead, the evidence for evolving dark energy from CMB, DESI BAO Year 1 and DES-SN5YR is only reduced from 3.9$\sigma$ to 3.3$\sigma$, consistent with the error budget. Finally, in this investigation, we identify an underestimated systematic uncertainty related to host galaxy property uncertainties, which could increase the final DES-SN5YR error budget by 3 per cent. In conclusion, we confirm the validity of the published DES-SN5YR results.
ISSN:13652966
00358711
DOI:10.1093/mnras/staf943