Protoplanets formed in a marginally gravitationally unstable (MGU) disk by either core accretion or disk instability will be subject to dynamical interactions with massive spiral arms, possibly resulting in inward or outward orbital migration, mergers with each other, or even outright ejection from the protoplanetary system. The latter process has been hypothesized as a possible formation scenario for the unexpectedly high frequency of unbound gas giant exoplanets (free floating planets, FFP). Previous calculations with the EDTONS fixed grid three dimensional (3D) hydrodynamics code found that protoplanets with masses from 0.01 $M_\oplus$ to 3 $M_{Jup}$ could undergo chaotic orbital evolutions in MGU disks for $\sim$ 1000 yrs without undergoing monotonic inward or outward migration. Here the Enzo 2.5 adaptive mesh refinement (AMR) 3D hydrodynamics code is used to follow the formation and orbital evolution of protoplanets in MGU disks for up to 2000 yrs. The Enzo results confirm the basic disk fragmentation results of the EDTONS code, as well as the absence of monotonic inward or outward orbital migration. In addition, Enzo allows protoplanet mergers to occur, unlike EDTONS, resulting in a significant decrease in the number of protoplanets that survive for 1000 to 2000 yrs in the Enzo models. These models also imply that gas giants should be ejected frequently in MGU disks that fragment into large numbers of protoplanets, supporting ejection as a possible source mechanism for the observed FFPs.
Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Dynamical Evidence of a Spiral-Arm-Driving and Gap-Opening Protoplanet from SAO 206462 Spiral Motion
基于甚大望远镜对 SAO 206462 原行星盘 7 年的观测，测得双螺旋臂旋转速率，推断存在一颗位于 66 au 处的原行星同时驱动螺旋臂并刻划缝隙，为原行星成像提供了理想目标。
Limits on Protoplanet Growth by Accretion of Small Solids
本文确定了一个小行星的核心（0.3 M $_{\oplus}$），吸积毫米大小的鹅卵石从气体盘的增长的限制。我们构建了随时间变化的球包络模型，该模型捕获了现有全球流体动力学模拟中不包括的物理过程，包括颗粒尺寸演变，尘埃运输和现实的气体状态方程。我们假设一个足够低的磁盘密度，卵石是边际耦合到气体，并被有效地捕获附近的核心邦迪半径。卵石然后迅速漂移，足以经历喷砂，相互碰撞和水冰升华的侵蚀。我们发现，卵石破碎是更有效的比灰尘重新粘。因此，需要建立一个质量> M $_{\oplus}$的核心的大卵石吸积率$\dot{M}_p$导致高包层金属丰度和颗粒不透明度。在$\dot{M}_p$ $\sim 10^{-7}$ M $_{\oplus}$ /yr以上，并且没有其他光度源，对流运动在邦迪半径附近扩展。温暖的，多尘的，和湍流的信封缓冲向内漂移卵石碎片：给定湍流浓度因子$f_{turb} \geq$ 1附近的低对流边界，核心增长率被限制为$1 \times 10^{-7} f_{turb}$ M $_{\oplus}$ /年和e折叠时间3 $f_{turb}^{-1}$百万年。剩余的固体碎片作为高度加工的硅酸盐排出。卵石冰永远不会到达核心，并且外壳含有相当数量的H2/He和金属。我们解释我们的结果，使用简单的稳定模型和半分析估计。未来的全球模拟，包括在这里建模的过程中，需要了解旋转和垂直磁盘结…
Testing a New Model of Embedded Protostellar Disks Against Observation: The Majority of Orion Class 0/I Disks Are Likely Warm, Massive, and Gravitationally Unstable
构建了基于内部吸积加热和临界引力不稳定假设的嵌入式原行星盘参数化模型，拟合 VANDAM 猎户座 156 个盘的多波长观测，发现多数 Class 0/I 盘温暖、大质量且星盘质量比接近 1。
