TY - JOUR
T1 - The radial orbit instability in collisionless N-body simulations
AU - Barnes, Eric I.
AU - Lanzel, Paul A.
AU - Williams, Liliya L.R.
PY - 2009
Y1 - 2009
N2 - 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.
AB - 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.
KW - Galaxies: Kinematics and dynamics
KW - Galaxies: Structure
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U2 - 10.1088/0004-637X/704/1/372
DO - 10.1088/0004-637X/704/1/372
M3 - Article
AN - SCOPUS:70449746897
SN - 0004-637X
VL - 704
SP - 372
EP - 384
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -