CosmoVerse Data Challenge: How Tip of the Red Giant Branch Analysis Choices Shape the Inferred Hubble Constant
Abstract
Tip of the red giant branch (TRGB)-based determinations of the Hubble constant (H0), the current expansion rate of the Universe, depend on choices made in selecting and analyzing stellar photometry and in assembling the sample of calibrator galaxies hosting Type Ia supernovae (SNe Ia). The CosmoVerse Data Challenge invites participants to analyze public photometric catalogs within a shared distance-ladder framework, opening each step of the measurement to the community and testing how these choices propagate into H0. Participants independently selected photometric catalogs, galaxies, and TRGB measurement settings, while using a common SN Ia compilation and fitting procedure to convert distances into H0. Supported by public notebooks and a training school, the challenge received 26 submissions from 22 participants. All submissions used the same analysis notebook, many participants were trainees at the school, and the true galaxy distances are unknown; the results therefore characterize the sensitivity of the submissions to analysis and sample-selection choices and are not a combined determination of H0 or an estimate of the systematic uncertainty in published TRGB measurements. The inferred H0 values have a median of 77.10 km s−1 Mpc−1 and a standard deviation of 7.38 km s−1 Mpc−1 (5.11 km s−1 Mpc−1 for the scaled median absolute deviation), ∼ 3.4 (∼ 2.4) times the typical quoted uncertainty of a submission. Differences in the measured tip of the anchor galaxy NGC 4258 add a coherent shift in the distance scale. The challenge shows how different choices within a common framework can produce substantially different values of H0, and provides an open basis for tracing these differences and for making datasets and tools more transparent and accessible.
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BibTeX
@misc{li2026cosmoverse,
title = {{CosmoVerse Data Challenge: How Tip of the Red Giant Branch Analysis Choices Shape the Inferred Hubble Constant}},
author = {Siyang Li and Eleonora Di Valentino and Jackson Levi Said and Kayla Owens and Yukei Murakami and Louise Breuval and Teresa Sicignano and Luis A. Escamilla and Jéferson A. S. Fortunato and Payam Ghafari and Ayush Hazarika and Vasiliki Karanasou and Trisha Khan and Yoelsy Leyva and Mahdi Najafi and Swayamtrupta Panda and Masroor C. Pookkillath and Antonio Quintana-Estellés and Masoume Reyhani and Nandan Roy and Chandra Shekhar Saraf and Rahul Shah and Jess Worsley and Alejandro Aguirre and Miguel Barroso Varela and Anupam Bhardwaj and Elliot Dutnall and Francesca Di Nella and Hussain Gohar and Paridhi Jain and Gracelynn Jost and Shivani Kulkarni and Dhiraj Kuniyal and Mariia Marinichenko and Yash Mehta and Vasudev Mittal and Lily Myers and Devaraja Mallesha Naik and José Antonio Nájera and Pilar Ruiz-Lapuente and Kathan Dave and Elaina Sadler and Gurnoor Sandhu and Sarang Shah and Petar Suman and Stefano Casertano and Alexei V. Filippenko and Richard Stiskalek and Syed Ashraf Uddin and Duško Borka and Vesna Borka Jovanović and Youri Carloni and Umut Demirbozan and Predrag Jovanović and Mohammad Malekjani and Nils A. Nilsson and Saeed Pourojaghi and Jorge Venzor and Lilia Anguelova and Marika Asgari},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05468},
eprint = {2611.05468},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05468},
}
RIS
TY - UNPB
TI - CosmoVerse Data Challenge: How Tip of the Red Giant Branch Analysis Choices Shape the Inferred Hubble Constant
AU - Siyang Li
AU - Eleonora Di Valentino
AU - Jackson Levi Said
AU - Kayla Owens
AU - Yukei Murakami
AU - Louise Breuval
AU - Teresa Sicignano
AU - Luis A. Escamilla
AU - Jéferson A. S. Fortunato
AU - Payam Ghafari
AU - Ayush Hazarika
AU - Vasiliki Karanasou
AU - Trisha Khan
AU - Yoelsy Leyva
AU - Mahdi Najafi
AU - Swayamtrupta Panda
AU - Masroor C. Pookkillath
AU - Antonio Quintana-Estellés
AU - Masoume Reyhani
AU - Nandan Roy
AU - Chandra Shekhar Saraf
AU - Rahul Shah
AU - Jess Worsley
AU - Alejandro Aguirre
AU - Miguel Barroso Varela
AU - Anupam Bhardwaj
AU - Elliot Dutnall
AU - Francesca Di Nella
AU - Hussain Gohar
AU - Paridhi Jain
AU - Gracelynn Jost
AU - Shivani Kulkarni
AU - Dhiraj Kuniyal
AU - Mariia Marinichenko
AU - Yash Mehta
AU - Vasudev Mittal
AU - Lily Myers
AU - Devaraja Mallesha Naik
AU - José Antonio Nájera
AU - Pilar Ruiz-Lapuente
AU - Kathan Dave
AU - Elaina Sadler
AU - Gurnoor Sandhu
AU - Sarang Shah
AU - Petar Suman
AU - Stefano Casertano
AU - Alexei V. Filippenko
AU - Richard Stiskalek
AU - Syed Ashraf Uddin
AU - Duško Borka
AU - Vesna Borka Jovanović
AU - Youri Carloni
AU - Umut Demirbozan
AU - Predrag Jovanović
AU - Mohammad Malekjani
AU - Nils A. Nilsson
AU - Saeed Pourojaghi
AU - Jorge Venzor
AU - Lilia Anguelova
AU - Marika Asgari
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05468
UR - https://arxiv.org/abs/2611.05468
AB - Tip of the red giant branch (TRGB)-based determinations of the Hubble constant (H_0), the current expansion rate of the Universe, depend on choices made in selecting and analyzing stellar photometry and in assembling the sample of calibrator galaxies hosting Type Ia supernovae (SNe Ia). The CosmoVerse Data Challenge invites participants to analyze public photometric catalogs within a shared distance-ladder framework, opening each step of the measurement to the community and testing how these choices propagate into H_0. Participants independently selected photometric catalogs, galaxies, and TRGB measurement settings, while using a common SN Ia compilation and fitting procedure to convert distances into H_0. Supported by public notebooks and a training school, the challenge received 26 submissions from 22 participants. All submissions used the same analysis notebook, many participants were trainees at the school, and the true galaxy distances are unknown; the results therefore characterize the sensitivity of the submissions to analysis and sample-selection choices and are not a combined determination of H_0 or an estimate of the systematic uncertainty in published TRGB measurements. The inferred H_0 values have a median of 77.10 km s^−1 Mpc^−1 and a standard deviation of 7.38 km s^−1 Mpc^−1 (5.11 km s^−1 Mpc^−1 for the scaled median absolute deviation), ∼ 3.4 (∼ 2.4) times the typical quoted uncertainty of a submission. Differences in the measured tip of the anchor galaxy NGC 4258 add a coherent shift in the distance scale. The challenge shows how different choices within a common framework can produce substantially different values of H_0, and provides an open basis for tracing these differences and for making datasets and tools more transparent and accessible.
ER -