2009/08/26 by Eric I. Barnes, Paul A. Lanzel, Liliya L. R. Williams · 6 citations
Physics and Astronomy · #Aerospace engineering #Anisotropy #Astrophysics #Astrophysics and Star Formation Studies #Classical mechanics #Gamma-ray bursts and supernovae #Instability #Isotropy #Mechanics #Optics #Orbit (dynamics) #Physics #Stellar, planetary, and galactic studies #Virial theorem #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/704/1/372
accepted for publication in ApJ. 9 figures in emulateapj style
arxiv created 2009/08/26 · openalex publication_date 2009/09/22 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using a suite of self-gravitating, collisionless N -body models, we systematically explore a parameter space relevant to the onset and behavior of the radial orbit instability (ROI), whose strength is measured by the systemic axis ratios of the models. We show that a combination of two initial conditions, namely the velocity anisotropy and the virial ratio, determines whether a system will undergo ROI and exactly how triaxial the system will become. A third initial condition, the radial shape of the density profile, plays a smaller, but noticeable role. Regarding the dynamical development of the ROI, the instability (1) begins after systems collapse to their most compact configuration and (2) evolves fastest when a majority of the particles have radially anisotropic orbits, while there is a lack of centrally concentrated isotropic orbits. We argue that this is further evidence that self-reinforcing torques are the key to the onset of the ROI. Our findings support the idea that a separate orbit instability plays a role in halting the ROI.