The stability of radially anisotropic rotating stellar systems with a central density cusp
Abstract
We investigate the interplay between radial velocity anisotropy and internal rotation in self-gravitating systems characterised by initial spherical symmetry and a moderate density cusp. We study the stability properties of such configurations to disentangle the impact of anisotropy, rotation, and density structure on the formation of triaxial stellar systems. We perform a set of collisionless N-body simulations starting from initial equilibria with a phase space distribution function of the class introduced by Osipkov and Merritt, modified to impose a net global angular momentum with the Lynden-Bell daemon protocol. We analyse the growth of the density and phase space distribution modes, as well as the axial ratios and triaxiality index of the final configurations. We find that internal rotation has a mitigating effect on the strength of the radial orbit instability in radially anisotropic models with \mbox{Fridman-Polyachenko-Shukhman} anisotropy index close to the consistency limit, while it slightly enhances the onset of the instability in marginally stable models. From the analysis of the growth rate of the density modes, we also find that an inner bar, which for maximally rotating initial conditions declines after its initial growth, is formed even in systems with initial profiles with a central density cusp.
Related
- Buchdahl type anisotropic stellar configurations in Rastall gravity
- Stellar Yields of Rapidly Rotating Population III Stars for the High Redshift Universe
- The JWST Ultramassive Galaxy Sample -- II. Supermassive Black Hole Masses for 8 Extreme Early-Type Galaxies via Jeans Anisotropic Modelling of High-Resolution Integral-Field NIRSpec Stellar Kinematics
- KiDS J1447-0149: The first spatially resolved spectroscopy of a relic galaxy beyond the local universe. An old high-dispersion core embedded in a compact rotating stellar structure
- Diversity of planetary origins and compositions traced by stellar abundance differences among co-natal star systems
BibTeX
@misc{cintio2026stability,
title = {{The stability of radially anisotropic rotating stellar systems with a central density cusp}},
author = {Pierfrancesco Di Cintio and Anna Lisa Varri},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.17763},
eprint = {2607.17763},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.17763},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The stability of radially anisotropic rotating stellar systems with a central density cusp
AU - Pierfrancesco Di Cintio
AU - Anna Lisa Varri
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2607.17763
UR - https://arxiv.org/abs/2607.17763
AB - We investigate the interplay between radial velocity anisotropy and internal rotation in self-gravitating systems characterised by initial spherical symmetry and a moderate density cusp. We study the stability properties of such configurations to disentangle the impact of anisotropy, rotation, and density structure on the formation of triaxial stellar systems. We perform a set of collisionless N-body simulations starting from initial equilibria with a phase space distribution function of the class introduced by Osipkov and Merritt, modified to impose a net global angular momentum with the Lynden-Bell daemon protocol. We analyse the growth of the density and phase space distribution modes, as well as the axial ratios and triaxiality index of the final configurations. We find that internal rotation has a mitigating effect on the strength of the radial orbit instability in radially anisotropic models with \mbox{Fridman-Polyachenko-Shukhman} anisotropy index close to the consistency limit, while it slightly enhances the onset of the instability in marginally stable models. From the analysis of the growth rate of the density modes, we also find that an inner bar, which for maximally rotating initial conditions declines after its initial growth, is formed even in systems with initial profiles with a central density cusp.
ER -