Dust Density Distribution and Imaging Analysis of Different Ice Lines in Protoplanetary Disks
Dust Density Distribution and Imaging Analysis of Different Ice Lines in Protoplanetary Disks
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DOI：
10.3847/1538-4357/aa7edb
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发表时间：
2017-07
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影响因子：
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通讯作者：
P. Pinilla;A. Pohl;S. Stammler;T. Birnstiel
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作者：
P. Pinilla;A. Pohl;S. Stammler;T. Birnstiel
最近对不同波长原行星盘的高角分辨率观测揭示了几种结构，包括多个亮环和暗环。嵌入式行星是这种结构最常用的解释，但也有其他模型能够像观测到的那样塑造环状尘埃。我们假设在Herbig恒星周围有一个圆盘，并研究了冰线对尘埃演化的影响，跟踪了覆盖从1 μm到2 m大小的物体的多种尘埃颗粒的生长、破碎和动力学。我们使用了破碎速度阈值的简化公式，假设它在一条、两条或三条冰线的位置呈径向变化。我们假设主要挥发物，特别是H2O， CO2和NH3在径向位置发生变化。利用所得的尘埃密度分布进行辐射传输计算，以便与当前的多波长观测结果进行比较。我们发现尘埃的结构密度分布和不同波长的径向强度强烈地依赖于盘的粘度。在冰线之间可以形成明显的发射间隙，并被环状结构包围，特别是在H2O和CO2（或CO）之间。与粒子捕获的模型预测相反，在毫米辐射下的间隙预计比在近红外辐射下的间隙更浅、更窄。在我们的模型中，总气体表面密度预计不会表现出强烈的变化，这与其他形成间隙的情景（如嵌入的巨行星或圆盘粘度的径向变化）相反。
Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that ice lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μm to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold, which is assumed to change radially at the location of one, two, or three ice lines. We assume changes at the radial location of main volatiles, specifically H2O, CO2, and NH3. Radiative transfer calculations are done using the resulting dust density distributions in order to compare with current multiwavelength observations. We find that the structures in the dust density profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between ice lines and be surrounded by ring-like structures, in particular between the H2O and CO2 (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface density is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.