A study of the high-inclination population in the Kuiper belt – I. The Plutinos

The dynamics of the high-inclination Plutinos is systematically studied. We first present the peculiar features of the 2: 3 Neptune mean motion resonance (NMMR) for inclined orbits, especially for the correlation of resonant amplitude A_ with inclination i. Using the numerical integrations for the age of the Solar system, the dynamical structure of the 2: 3 NMMR is mapped out on the plane of semi-major axis versus i for different eccentricities. We have shown that i of stable resonant orbits could be as high as 90 deg; and the stable region is roughly surrounded by the contours of A_ = 120 deg. These new findings allow us to further explore the 2: 3 NMMR capture and retention of planetesimals with initial inclinations i0 = 48 deg, their i are forced to decrease throughout the outward migration; (3) Plutinos with i > 48 deg are certainly outside the Kozai mechanism, since an inclination increase is prohibited by the migrating 2: 3 NMMR; (4) The 7: 11 inclination-type NMMR could be responsible for nearly-circular Plutinos, and a minimum i0 ~ 15 deg is required to intrigue this mechanism.