Quantitative Morphological Fingerprints of Yarkovsky-YORP Co-evolution in Asteroid Families

Abstract: The "V-shaped" distributions observed in asteroid families are dynamic fingerprints of the long-term interplay between the Yarkovsky and YORP effects, yet their detailed morphology has largely remained qualitatively described. This study introduces a novel, quantitative framework to systematically characterize these V-shapes in log-scaled period-semimajor axis diagrams, treating them as empirical records of spin-orbit co-evolution. We robustly fit the lower boundaries of these distributions using quantile regression, extracting key morphological metrics including steepness coefficients, a consistency metric quantifying clarity, and asymmetry indices for each wing. Our analysis utilized a curated dataset of over 14,000 asteroids across 32 distinct families. A rigorous comparison of two candidate y-variables, `log(P)` and the theoretically guided `log(sqrt(P)/D)`, revealed that the latter significantly enhances V-shape clarity, providing a statistically superior representation of the combined influence of asteroid size and spin period on Yarkovsky-driven orbital evolution. Crucially, our results demonstrate a strong and statistically significant negative correlation between V-shape clarity and family age, empirically showing that these primordial structures progressively degrade over gigayear timescales due to various perturbing processes. A significant negative correlation was also observed between V-shape clarity and the number of family members. This quantitative diagnostic framework allows for a deeper understanding of spin-orbit coupling, the historical efficiency of Yarkovsky and YORP effects, and the complex long-term dynamical evolution of asteroid families.

Subjects:	astro-ph.EP; physics.space-ph
Cite as:	PX:2508.00064