High-inclination Centaur reservoirs beyond Neptune

Abstract

(Abridged) Numerical simulations of the past evolution of high-inclination Centaurs showed they originated from orbits beyond Neptune that were perpendicular to the Solar System's invariable plane in a region called the polar corridor. Recently, a study of Centaur injection in the three-body problem showed that Neptune-crossing TNOs in the polar corridor in the range [40:160] au have dynamical times that exceed the Solar System's age suggesting the presence of long-lived Centaur-producing reservoirs. We demonstrate the existence of such reservoirs in the Solar System by simulating the TNOs' time-forward evolution in the presence of the giant planets, the Galactic tide and passing stars using the IAS15 integrator of the REBOUND and REBOUNDx packages. We also assess the efficiency of Centaur injection as a function of the initial inclination and determine if high-inclination Centaurs may be produced by low inclination reservoirs. We find that TNO reservoirs in the semi-major axis range [50:140] au are long-lived and their populations peak at the Tisserand parameters T=0.5 and T=-1.5. Saturn is found to induce secondary structures in the polar corridor by holding the perihelia of a fraction of high-inclination reservoir material. We find that the Centaur inclination at minimum semi-major axis depends linearly on the Tisserand parameter regardless of the initial semi-major axis. Its amplitude shows that low inclination reservoirs such as the early protoplanetary disk are unlikely to produce high-inclination Centaurs in contrast to reservoirs in the polar corridor. We identified the likely location of the closest reservoirs to Neptune populated by TNOs captured in the early Solar System that produce high-inclination Centaurs. The Legacy Survey of Space and Time will be able to constrain the reservoirs' extent and population size