Testing Refracted Gravity with the kinematics of stacked galaxy clusters
Abstract
We test Refracted Gravity (RG), a phenomenological modified gravity model that modifies the Poisson equation by introducing an effective gravitational permittivity ε(ρbar) which depends on the baryonic matter density ρbar and mimics the behaviour of dark matter in cosmic structures. We perform a kinematical analysis of member galaxies for a sample of 74 galaxy clusters, compiled from the Cluster Infall Regions in the Sloan Digital Sky Survey (CIRS). We stack the clusters in three bins of increasing velocity dispersion to mitigate the effects of systematic errors induced by deviations from dynamical equilibrium and from the assumption of spherical symmetry. By means of the \texttt{MG-MAMPOSSt} code, we reconstruct the gravitational potential in RG and infer the model parameters jointly with the gas and stellar mass-profile parameters, adopting broad, physically informed priors on the baryonic components. The estimates of the main parameter in Refracted Gravity, the vacuum permittivity ε0, range from $0.04$ to $0.37$, across the three main stacks, depending on the model adopted for the hot gas component. The constraints are mutually compatible within the quoted uncertainties and overlap with previous cluster-scale estimates. The agreement becomes less sensitive to gas parametrisation when selecting the less-disturbed clusters for building the stacks. These results characterize the sensitivity of cluster-scale RG constraints to baryonic modelling and sample selection
Related
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- Testing the Stellar Feedback-driven Breathing Mode in Low-mass Galaxies with Gas Kinematics
BibTeX
@misc{primignani2026testing,
title = {{Testing Refracted Gravity with the kinematics of stacked galaxy clusters}},
author = {Dario Primignani and Lorenzo Pizzuti and Antonaldo Diaferio and Valeria Broccolato},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.06841},
eprint = {2610.06841},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.06841},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Testing Refracted Gravity with the kinematics of stacked galaxy clusters
AU - Dario Primignani
AU - Lorenzo Pizzuti
AU - Antonaldo Diaferio
AU - Valeria Broccolato
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2610.06841
UR - https://arxiv.org/abs/2610.06841
AB - We test Refracted Gravity (RG), a phenomenological modified gravity model that modifies the Poisson equation by introducing an effective gravitational permittivity ε(ρ_bar) which depends on the baryonic matter density ρ_bar and mimics the behaviour of dark matter in cosmic structures. We perform a kinematical analysis of member galaxies for a sample of 74 galaxy clusters, compiled from the Cluster Infall Regions in the Sloan Digital Sky Survey (CIRS). We stack the clusters in three bins of increasing velocity dispersion to mitigate the effects of systematic errors induced by deviations from dynamical equilibrium and from the assumption of spherical symmetry. By means of the \texttt{MG-MAMPOSSt} code, we reconstruct the gravitational potential in RG and infer the model parameters jointly with the gas and stellar mass-profile parameters, adopting broad, physically informed priors on the baryonic components. The estimates of the main parameter in Refracted Gravity, the vacuum permittivity ε_0, range from $0.04$ to $0.37$, across the three main stacks, depending on the model adopted for the hot gas component. The constraints are mutually compatible within the quoted uncertainties and overlap with previous cluster-scale estimates. The agreement becomes less sensitive to gas parametrisation when selecting the less-disturbed clusters for building the stacks. These results characterize the sensitivity of cluster-scale RG constraints to baryonic modelling and sample selection
ER -