Efficient numerical evolution of self-gravitating systems with dark-matter-baryon scattering

@misc{kamionkowski2026efficient,
  title = {{Efficient numerical evolution of self-gravitating systems with dark-matter-baryon scattering}},
  author = {Marc Kamionkowski and Vera Gluscevic and Kris Sigurdson},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.20702},
  eprint = {2610.20702},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.20702},
}

TY  - UNPB
TI  - Efficient numerical evolution of self-gravitating systems with dark-matter-baryon scattering
AU  - Marc Kamionkowski
AU  - Vera Gluscevic
AU  - Kris Sigurdson
PY  - 2026
DA  - 2026/10/14
PB  - arXiv
DO  - 10.48550/arxiv.2610.20702
UR  - https://arxiv.org/abs/2610.20702
AB  - We present a fast algorithm to numerically evolve a spherically symmetric system consisting of dark matter and gas, including dark-matter-baryon scattering. The method augments the spherical N-body code NSphere, which collapses the six-dimensional phase space of a spherical collisionless system to three dimensions, with a one-dimensional Lagrangian treatment of gas. Dark-matter-baryon scattering is implemented as a Monte-Carlo process between the dark-matter numerical particles and the gas shells. We also implement an algorithm for radiative gas cooling that is valid for weak cooling. The gas, as well as dark-matter-baryon scattering and cooling, adds only incrementally to the run time of the code, allowing systems to be evolved on a laptop computer, a tiny fraction of the computational resources required for a full 3D N-body/hydro simulation. To illustrate, we show the evolution of a ∼ 10^13 M_⊙ halo with a dark-matter-baryon scattering cross section σ_tot/m_χ=0.1 cm^2 g^−1 but no gas cooling. We then show examples with radiative gas cooling where the cooling is altered through interaction with dark-matter particles. The resulting code, NSphere-IDM, allows the implications of dark-matter interactions for galaxy evolution to be explored quickly over large volumes of the dark-matter parameter space, and other new physics (e.g., dark-matter self-interactions or anisotropy in the distribution function) is easily incorporated. The code can also provide useful calibrations and benchmarks for fully 3D N-body or hydrodynamical simulations.
ER  -