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arXiv 0906.5524astro-ph.EP
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碎片盘的垂直结构

Vertical structure of debris discs

Philippe Thebault

摘要:

碎片盘的垂直厚度经常被用作衡量这些系统的动力学激发的尺度,并作为发现隐藏的大质量扰动(如行星胚胎)的线索。然而,这个论点可能是有缺陷的,因为观测到的尘埃应该是在辐射压力和相互碰撞的共同作用下自然地被放置在倾斜的轨道上。我们严格地重新调查这个问题,并在没有任何额外的扰动体的情况下,数值估计碰撞演化盘的“自然”垂直厚度是多少。我们使用一个确定性的碰撞代码,以下人口的坚不可摧的测试颗粒遭受相互非弹性影响的动态演化。计算中考虑了晶粒尺寸的差异以及辐射压力的影响。我们发现,在辐射压力和碰撞的耦合作用下,晶粒自然地获得几度的倾角。光盘分层相对于晶粒尺寸,最小的晶粒具有最大的垂直分散和较大的聚集更接近中平面。碎片盘在可见光至中红外波长处应具有最小的“自然”观测纵横比$h_{min}\sim 0.04\pm0.02$,在该波长处,通量主要由最小的结合颗粒决定。这些值与许多垂直分辨碎片盘的估计厚度相当,如AU Mic的具体例子所示。对于所有具有$h \sim h_{min}$的系统,不能从盘的垂直色散推断出嵌入扰动体的存在(或不存在

英文摘要:

The vertical thickness of debris discs is often used as a measure of these systems' dynamical excitation and as clues to the presence of hidden massive perturbers such as planetary embryos. However, this argument could be flawed because the observed dust should be naturally placed on inclined orbits by the combined effect of radiation pressure and mutual collisions. We critically reinvestigate this issue and numerically estimate what the "natural" vertical thickness of a collisionally evolving disc is, in the absence of any additional perturbing body. We use a deterministic collisional code, following the dynamical evolution of a population of indestructible test grains suffering mutual inelastic impacts. Grain differential sizes as well as the effect of radiation pressure are taken into account. We find that, under the coupled effect of radiation pressure and collisions, grains naturally acquire inclinations of a few degrees. The disc is stratified with respect to grain sizes, with the smallest grains having the largest vertical dispersion and the bigger ones clustered closer to the midplane. Debris discs should have a minimum "natural" observed aspect ratio $h_{min}\sim 0.04\pm0.02$ at visible to mid-IR wavelengths where the flux is dominated by the smallest bound grains. These values are comparable to the estimated thicknesses of many vertically resolved debris discs, as is illustrated with the specific example of AU Mic. For all systems with $h \sim h_{min}$, the presence (or absence) of embedded perturbing bodies cannot be inferred from the vertical dispersion of the disc

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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