Dynamical friction vs. subhalo heating in Cold Dark Matter haloes
Abstract
The orbital evolution of massive stellar systems embedded in dark matter haloes is governed by competing processes. Dynamical friction removes orbital energy, whereas fluctuations in the gravitational field generated by dark matter subhaloes inject energy through stochastic heating. We investigate the balance between these two mechanisms using analytical arguments and numerical experiments. We show that, for a given host halo and subhalo population, there exists a critical mass Mcrit at which heating and friction balance. Clusters with masses Mcl>Mcrit lose orbital energy and sink towards the centre of the halo, whereas those with Mcl<Mcrit gain energy and expand outwards. At Mcl≃ Mcrit, the two processes balance, leading to a cluster population that, on average, neither sinks nor expands within the host halo. In CDM haloes, the critical mass is primarily controlled by the upper end of the subhalo mass function. Since massive subhaloes are intrinsically rare, the balance between heating and friction shows substantial halo-to-halo scatter. For dark matter haloes in the mass range associated with dwarf spheroidal galaxies (dSphs), we find Mcrit≳ 105M⊙, comparable to the masses of globular clusters in the Fornax dSph. Stochastic heating by dark substructure may therefore significantly delay the orbital decay of globular clusters and help alleviate the Fornax timing problem.
Related
- 21-cm Constraints on S-wave Dark Matter Annihilation with Subhalo-enhanced Effects
- Strong Constraints on Line Signals from Dark Matter Annihilation in a Nearby Subhalo
- Polar coordinate transformations for machine-learning-based dark matter subhalo detection in strong gravitational lenses
- Point spread function requirements for dark matter subhalo detection with the Habitable Worlds Observatory
- Scatter, bias, and chaos of satellite orbits in triaxial dark matter haloes
BibTeX
@misc{penarrubia2026dynamical,
title = {{Dynamical friction vs. subhalo heating in Cold Dark Matter haloes}},
author = {Jorge Peñarrubia and Pierfrancesco Di Cintio and Eduardo Vitral and Matthew G. Walker},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36796},
eprint = {2609.36796},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36796},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Dynamical friction vs. subhalo heating in Cold Dark Matter haloes
AU - Jorge Peñarrubia
AU - Pierfrancesco Di Cintio
AU - Eduardo Vitral
AU - Matthew G. Walker
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.36796
UR - https://arxiv.org/abs/2609.36796
AB - The orbital evolution of massive stellar systems embedded in dark matter haloes is governed by competing processes. Dynamical friction removes orbital energy, whereas fluctuations in the gravitational field generated by dark matter subhaloes inject energy through stochastic heating. We investigate the balance between these two mechanisms using analytical arguments and numerical experiments. We show that, for a given host halo and subhalo population, there exists a critical mass M_crit at which heating and friction balance. Clusters with masses M_cl>M_crit lose orbital energy and sink towards the centre of the halo, whereas those with M_cl<M_crit gain energy and expand outwards. At M_cl≃ M_crit, the two processes balance, leading to a cluster population that, on average, neither sinks nor expands within the host halo. In CDM haloes, the critical mass is primarily controlled by the upper end of the subhalo mass function. Since massive subhaloes are intrinsically rare, the balance between heating and friction shows substantial halo-to-halo scatter. For dark matter haloes in the mass range associated with dwarf spheroidal galaxies (dSphs), we find M_crit≳ 10^5M_⊙, comparable to the masses of globular clusters in the Fornax dSph. Stochastic heating by dark substructure may therefore significantly delay the orbital decay of globular clusters and help alleviate the Fornax timing problem.
ER -