Searching for Dense Perturbers in Cold Dark Matter Simulations
Abstract
Recently, several low-mass, dense perturbers have been inferred from astrophysical observations of gravitational lensing, stellar streams, and satellite galaxies. If interpreted as dark matter subhalos, their inner densities exceed the predictions of the standard cold dark matter (CDM) model. We systematically investigate this tension using a CDM-only zoom-in simulation of a Milky Way analog. We analyze more than 5000 subhalos with masses down to 106 M⊙ and reconstruct their inner density profiles using a tidal truncation model. The simulated subhalos are then compared with the observed compact perturbers in terms of their density profiles, enclosed masses, concentrations, and projected cylindrical masses. None of the simulated CDM subhalos is sufficiently dense to reproduce the inferred mass distributions of the observed perturbers. We further examine the redshift evolution of subhalo concentrations and derive a fitting function to characterize this evolution. Our findings motivate further investigations into exceptionally rare formation histories that could produce such dense perturbers, as well as the possibility of physics beyond the standard CDM model.
Related
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BibTeX
@misc{zhang2026searching,
title = {{Searching for Dense Perturbers in Cold Dark Matter Simulations}},
author = {Xingyu Zhang and Hai-Bo Yu and Demao Kong and Ethan O. Nadler},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27236},
eprint = {2610.27236},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27236},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Searching for Dense Perturbers in Cold Dark Matter Simulations
AU - Xingyu Zhang
AU - Hai-Bo Yu
AU - Demao Kong
AU - Ethan O. Nadler
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.27236
UR - https://arxiv.org/abs/2610.27236
AB - Recently, several low-mass, dense perturbers have been inferred from astrophysical observations of gravitational lensing, stellar streams, and satellite galaxies. If interpreted as dark matter subhalos, their inner densities exceed the predictions of the standard cold dark matter (CDM) model. We systematically investigate this tension using a CDM-only zoom-in simulation of a Milky Way analog. We analyze more than 5000 subhalos with masses down to 10^6 M_⊙ and reconstruct their inner density profiles using a tidal truncation model. The simulated subhalos are then compared with the observed compact perturbers in terms of their density profiles, enclosed masses, concentrations, and projected cylindrical masses. None of the simulated CDM subhalos is sufficiently dense to reproduce the inferred mass distributions of the observed perturbers. We further examine the redshift evolution of subhalo concentrations and derive a fitting function to characterize this evolution. Our findings motivate further investigations into exceptionally rare formation histories that could produce such dense perturbers, as well as the possibility of physics beyond the standard CDM model.
ER -