Are Irregular Satellite Systems Shaped by Secular Resonances?
M. Cuk, J. A. Burns, V. Carruba (Cornell U.) In order to explore how the irregular satellites are distributed through the orbital phase space criss-crossed by secular resonances, we numericaly surveyed secular behavior for a wide range of semimajor axes, eccentricities and inclinations i. We observed that the minimum inclination for Kozai resonance is not uniformly 39.2\circ (Innanen et al. 1997) but instead depends significantly on mean motion n. We found the critical inclination icrit to be lower (closer to the reference plane) for distant retrograde satellites but higher for prograde ones. We corrected Innanen et al.’s formulae for {\dot \omega} and {\dot \Omega} by incorporating terms (Saha and Tremaine 1993) of third and higher orders in n to {\dot \varpi}. Thus corrected, the new icrit agrees with both our numerical survey and simulations of observed satellites. The irregular satellite orbits seem to be grouped about this modified icrit in a-i space. This clustering includes all
