自由漂浮行星的银河动力学：从抛射踢到微引力透镜
The Galactic Dynamics of Free-Floating Planets: From Ejection Kicks to Microlensing
- University of California, Santa Cruz（加州大学圣克鲁兹分校）
- Université de Montréal（蒙特利尔大学）
- Mila – Quebec Artificial Intelligence Institute（米拉-魁北克人工智能研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过模拟$10^6$个自由漂浮行星在银河势中的演化，发现抛射踢对动力学加热的贡献小于初始盘演化，并识别出质量依赖的位移差异，为微引力透镜观测提供预测。
AI中文摘要：
自由漂浮行星（FFP）可能保留将其从宿主系统中抛射出来的机制的动力学子印记。我们在静态、唯象的银河势中，对$10^6$个无碰撞FFP测试粒子进行了$10^8$年的积分，将质量无关的踢模型与质量耦合处方（$\sigma_{\rm CB}\propto M^{-0.15}$，$v_{\rm PL}\propto M^{-0.5}$）与匹配的无踢对照组进行了比较。在注入时恢复了所施加的质量依赖性，组合通道的中值耦合踢在五个质量区间内从$10.716$降至$0.708~{\rm km\\\\,s^{-1}}$，相差约$\sim15.1$倍。在100~Myr的银河传播后，匹配的踢与对照位移中仍可见质量依赖趋势，其同一区间的中值从$0.7001$降至$0.0539$~kpc。剩余的数值差异集中在质量分辨的微分位移中，而非整体相空间矩：零踢和耦合踢群体的最终速度弥散几乎相同，只有百分之几的粒子离开所采用的盘区域，并且满足正式银河非束缚判据（$E_i>0$）的粒子比例在我们报告的每个诊断中均可忽略。将每个踢群体与其匹配的无踢对照进行比较表明，大部分整体动力学加热源于初始温暖、非平衡盘的演化，而非抛射踢本身，从而分离出踢的较小贡献。
英文摘要：
Free-floating planets (FFPs) may retain dynamical signatures of the mechanisms that eject them from their host systems. We integrate $10^6$ collisionless FFP test particles for $10^8$~yr in a static, phenomenological Galactic potential, comparing a mass-independent kick model with a mass-coupled prescription ($σ_{\rm CB}\propto M^{-0.15}$, $v_{\rm PL}\propto M^{-0.5}$) against a matched no-kick control. The imposed mass dependence is recovered at injection, with the combined-channel median coupled kick decreasing from $10.716$ to $0.708~{\rm km\,s^{-1}}$ across five mass bins---a factor of $\sim15.1$. A mass-dependent trend remains visible after $100$~Myr of Galactic propagation in the matched kicked-versus-control displacement, whose median decreases from $0.7001$ to $0.0539$~kpc across the same bins. The remaining numerical distinction is concentrated in this mass-resolved differential displacement rather than in the bulk phase-space moments: the final velocity dispersions of the null and coupled kicked populations are nearly identical, only a few percent of particles leave the adopted disk region, and the fraction of particles satisfying the formal Galactic-unbound criterion ($E_i>0$) remains negligible in every diagnostic we report. Comparing each kicked population against its matched no-kick control shows that much of the overall kinematic heating arises from the evolution of the initially warm, nonequilibrium disk rather than from the ejection kick itself, isolating the kick's smaller contribution.
