VELOCITY-DEPENDENT CATASTROPHIC DISRUPTION CRITERIA FOR PLANETESIMALS
VELOCITY-DEPENDENT CATASTROPHIC DISRUPTION CRITERIA FOR PLANETESIMALS
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DOI：
10.1088/0004-637x/691/2/l133
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发表时间：
2009-02
期刊：
影响因子：
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通讯作者：
S. Stewart;Z. Leinhardt
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文献类型：
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作者：
S. Stewart;Z. Leinhardt
在行星形成过程中，星子对碰撞侵蚀的抵抗力发生巨大变化。碰撞中吸积和侵蚀之间的转变由最大残余物质量（Mlr）和归一化比撞击能（Q/Q*D）之间的关系定义，其中Q*D是与尺寸相关的灾难性破坏标准（使目标质量一半分散所需的Q值）。在此，我们计算了受低速碰撞（1 - 300米/秒）影响的引力束缚聚集体的Q*D，并将结果与先前在高速下的研究进行比较。我们发现Q*D根据撞击速度和材料特性有数量级的变化。我们定义了新的变量来描述灾难性破坏，消除了传统变量（Q和目标半径）中固有的模糊性（关于材料密度和抛射体与目标质量比）：RC1是在1克/立方厘米密度下抛射体和目标质量总和（Mtot）的球半径，QR是0.5μV2i/Mtot（μ是约化质量，Vi是撞击速度），Q*RD是使总质量一半分散所需的QR。我们推导出最大残余物的一个通用定律，Mlr/Mtot = -0.5(QR/Q*RD - 1) + 0.5，以及用于行星形成数值研究的强星子和弱星子的与速度相关的灾难性破坏标准。由于在低速碰撞期间有效的动量耦合，弱聚集体很容易被破坏。星子的碰撞增长需要一个动力学上寒冷的环境；或者，需要一种非碰撞机制来形成足够大以抵抗碰撞破坏（几十千米）的星子。
The resistance of planetesimals to collisional erosion changes dramatically during planet formation. The transition between accretion and erosion from a collision is defined by the relationship between the mass of the largest remnant (Mlr) and the normalized specific impact energy (Q/Q*D), where Q*D are the size-dependent catastrophic disruption criteria (the Q required to disperse half the target mass). Here, we calculate Q*D for gravitationally bound aggregates subject to low-velocity collisions (1–300 m s−1) and compare the results to previous work at high velocities. We find that Q*D varies by orders of magnitude depending on the impact velocity and material properties. We define new variables to describe catastrophic disruption that remove ambiguities (over material density and projectile-to-target mass ratio) that are inherent in the traditional variables (Q and target radius): RC1 is the spherical radius of the combined projectile and target masses (Mtot) at a density of 1 g cm−3, QR is 0.5μV2i/Mtot (μ is the reduced mass and Vi is the impact velocity), and Q*RD is the QR required to disperse half the combined mass. We derive a universal law for the largest remnant, Mlr/Mtot = −0.5(QR/Q*RD − 1) + 0.5, and velocity-dependent catastrophic disruption criteria for strong and weak planetesimals for use in numerical studies of planet formation. Weak aggregate bodies are easily disrupted due to efficient momentum coupling during low-velocity collisions. Collisional growth of planetesimals requires a dynamically cold environment; alternatively, a noncollisional mechanism is required to form planetesimals large enough to be resistant to collisional disruption (several tens of kilometers).