On the Long-Term Orbital Behaviour of Hilda Asteroids - I. Global Stability Patterns and Catalogue

The Hildas are objects trapped in 3:2 mean-motion resonance (MMR) with Jupiter, and are a fascinating window into the Solar system's formation and evolution. We present the results of detailed dynamical integrations of 2,699 numbered asteroids in the Hilda region, following 243 clones of each Hilda for 1 Gyr under the influence of the giant planets and the Sun; 54.7% of our sample exhibit extreme dynamical stability, with all clones of 1,475 Hildas remaining trapped in the 3:2 MMR for the full 1 Gyr of our integrations. A further 408 Hildas (15.1% of the sample) see more than 50% of their clones surviving within the MMR at the end of the simulations. Of the remaining 30.2% of the population, 327 objects (12.1%) lose 50% of their clones at some point between the 100 Myr and 1 Gyr point, leading to dynamical half-lives measured in hundreds of millions of years -- a result compatible with those objects being members of a once larger population of Hildas trapped since the Solar system's youth. The final 489 objects (18.12%) prove highly unstable -- and may well be interlopers, captured to the Hilda population in the relatively recent past. Overall, our results suggest that the Hilda population was larger in the past, while its remarkably high stability over Gyr timescales is consistent with a primordial origin.