Probing dynamics of extreme galaxies I. Dark matter content in ultra-diffuse galaxies
Abstract
We investigate the internal structure of two galaxies from the LEWIS sample: the ultra-diffuse galaxy UDG-1 and the extended dwarf LSB-6. Both show coherent stellar rotation combined with a non-negligible fraction of random motion, with no signs of ongoing disturbance. This is the first attempt to constrain the dynamics and dark matter physics of rotation-supported UDGs through integral-field stellar kinematics. We model the galaxies as stellar spheroids with typical dwarf-like thickness embedded in spherical dark matter halos, deriving two-dimensional velocity fields that we compare with the observations in a Bayesian framework. Besides cold dark matter, we test fuzzy, self-interacting, and non-minimally coupled dark matter. The data prefer a cuspy halo in UDG-1 and a cuspless one in LSB-6. All the alternative models remain viable, although current data cannot conclusively discriminate among them. For fuzzy dark matter we obtain mutually consistent boson masses, mα= 4.7+1.8−1.1 × 10−22 eV for UDG-1 and mα= 6.3+0.4−0.4 × 10−22 eV for LSB-6. For self-interacting dark matter, LSB-6 yields a robust constraint on the velocity-weighted cross section, ⟨ σv⟩/m = 14.3+2.0−1.9 cm2 km g−1 s−1. For non-minimally coupled dark matter we derive upper bounds on the coupling length, implying marginal deviations from ΛCDM. Regardless of the model, both galaxies exhibit a dark matter content comparable with halos of typical dwarf galaxies with similar stellar masses. Together with stellar population analyses and globular cluster information, these results support a scenario in which UDG-1 and LSB-6 originate from puffed-up dwarfs. This work is the first in a series exploiting kinematic data of extremely low-surface-brightness galaxies to test fundamental physics, from dark matter to modified theories of gravity.
Versions
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BibTeX
@misc{bouche2026probing,
title = {{Probing dynamics of extreme galaxies I. Dark matter content in ultra-diffuse galaxies}},
author = {Filippo Bouchè and Chiara Buttitta and Saboura Zamani and Enrichetta Iodice and Salvatore Capozziello and Vincenzo Salzano and Marcello Miranda and Enrico Maria Corsini and Marco Mirabile},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10700},
eprint = {2609.10700},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10700},
}
RIS
TY - UNPB
TI - Probing dynamics of extreme galaxies I. Dark matter content in ultra-diffuse galaxies
AU - Filippo Bouchè
AU - Chiara Buttitta
AU - Saboura Zamani
AU - Enrichetta Iodice
AU - Salvatore Capozziello
AU - Vincenzo Salzano
AU - Marcello Miranda
AU - Enrico Maria Corsini
AU - Marco Mirabile
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10700
UR - https://arxiv.org/abs/2609.10700
AB - We investigate the internal structure of two galaxies from the LEWIS sample: the ultra-diffuse galaxy UDG-1 and the extended dwarf LSB-6. Both show coherent stellar rotation combined with a non-negligible fraction of random motion, with no signs of ongoing disturbance. This is the first attempt to constrain the dynamics and dark matter physics of rotation-supported UDGs through integral-field stellar kinematics. We model the galaxies as stellar spheroids with typical dwarf-like thickness embedded in spherical dark matter halos, deriving two-dimensional velocity fields that we compare with the observations in a Bayesian framework. Besides cold dark matter, we test fuzzy, self-interacting, and non-minimally coupled dark matter. The data prefer a cuspy halo in UDG-1 and a cuspless one in LSB-6. All the alternative models remain viable, although current data cannot conclusively discriminate among them. For fuzzy dark matter we obtain mutually consistent boson masses, m_α= 4.7^+1.8_−1.1 × 10^−22 eV for UDG-1 and m_α= 6.3^+0.4_−0.4 × 10^−22 eV for LSB-6. For self-interacting dark matter, LSB-6 yields a robust constraint on the velocity-weighted cross section, ⟨ σv⟩/m = 14.3^+2.0_−1.9 cm^2 km g^−1 s^−1. For non-minimally coupled dark matter we derive upper bounds on the coupling length, implying marginal deviations from ΛCDM. Regardless of the model, both galaxies exhibit a dark matter content comparable with halos of typical dwarf galaxies with similar stellar masses. Together with stellar population analyses and globular cluster information, these results support a scenario in which UDG-1 and LSB-6 originate from puffed-up dwarfs. This work is the first in a series exploiting kinematic data of extremely low-surface-brightness galaxies to test fundamental physics, from dark matter to modified theories of gravity.
ER -