Debiasing Local Cluster Infall Reveals H0: Application to the Virgo Cluster
Abstract
Galaxy recession velocities are commonly used to measure the Hubble constant, H0, with peculiar velocities treated as random noise. Around massive clusters, however, these motions can be predicted by the gravitational potential of the central halo, allowing them to be modeled rather than averaged over. Past analyses relied on analytic approximations for the distance-infall-velocity relation, whose accuracy has not been tested using realistic cosmological simulations. We use halos from the IllustrisTNG simulation to quantify the bias and precision of several commonly used Hubble-flow models. We find that widely used fitting functions systematically underestimate H0, whereas the full analytical solution reduces but does not eliminate these biases. We develop a simulation-based method to infer H0 and apply it to TRGB distance samples around the Virgo Cluster. We find H0=74.4± 2.9 and 73.4± 3.9 km s−1 Mpc−1 (stat) for the minor and the major infall models, respectively. Correcting for the bias calibrated on TNG halos, these measurements raise the value of H0 to 81.6 ± 7.8 and 87.3 ± 8.8 km s−1 Mpc−1 (stat+sys), where the minor infall model has the smallest bias from the Virgo mocks. We show that statistical errors are dominated by the residual velocity scatter around the infall model, while systematic errors are dominated by the transformation to the structure's comoving frame and halo population variance. These results establish a framework for interpreting cluster infall measurements and explain trends in previous H0 inferences.
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BibTeX
@misc{carreres2026debiasing,
title = {{Debiasing Local Cluster Infall Reveals $\boldsymbolH_0$: Application to the Virgo Cluster}},
author = {Bastien Carreres and David Benisty and Jenny Wagner and Avery Erlenbach and Dan Scolnic and Adam Riess},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10779},
eprint = {2610.10779},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10779},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Debiasing Local Cluster Infall Reveals H_0: Application to the Virgo Cluster
AU - Bastien Carreres
AU - David Benisty
AU - Jenny Wagner
AU - Avery Erlenbach
AU - Dan Scolnic
AU - Adam Riess
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10779
UR - https://arxiv.org/abs/2610.10779
AB - Galaxy recession velocities are commonly used to measure the Hubble constant, H_0, with peculiar velocities treated as random noise. Around massive clusters, however, these motions can be predicted by the gravitational potential of the central halo, allowing them to be modeled rather than averaged over. Past analyses relied on analytic approximations for the distance-infall-velocity relation, whose accuracy has not been tested using realistic cosmological simulations. We use halos from the IllustrisTNG simulation to quantify the bias and precision of several commonly used Hubble-flow models. We find that widely used fitting functions systematically underestimate H_0, whereas the full analytical solution reduces but does not eliminate these biases. We develop a simulation-based method to infer H_0 and apply it to TRGB distance samples around the Virgo Cluster. We find H_0=74.4± 2.9 and 73.4± 3.9 km s^−1 Mpc^−1 (stat) for the minor and the major infall models, respectively. Correcting for the bias calibrated on TNG halos, these measurements raise the value of H_0 to 81.6 ± 7.8 and 87.3 ± 8.8 km s^−1 Mpc^−1 (stat+sys), where the minor infall model has the smallest bias from the Virgo mocks. We show that statistical errors are dominated by the residual velocity scatter around the infall model, while systematic errors are dominated by the transformation to the structure's comoving frame and halo population variance. These results establish a framework for interpreting cluster infall measurements and explain trends in previous H_0 inferences.
ER -