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arXiv 2109.02652astro-ph.GAastro-ph.SR
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年轻过渡盘WL 17的亚结构探测

Detection of Substructures in Young Transition Disk WL 17

Hannah Gulick, Sarah Sadavoy, Luca Matra, Patrick Sheehan, Nienke van der Marel

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Accepted to ApJ, 13 pages, 6 figures
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摘要：

WL 17是蛇夫座L1688分子云复合体中的一个年轻的过渡盘。尽管WL 17是L1688中最明亮的圆盘之一，并且质量足以预期尘埃自散射，但它在ALMA仪器灵敏度极限下的偏振中未被检测到。如此低的偏振分数可以指示光束内未分辨的偏振或光学上薄的尘埃发射。我们测试后一种情况下，结合高灵敏度233 GHz的斯托克斯我的偏振观测数据与以前的ALMA数据在345 GHz和100 GHz。我们使用简单的几何形状，以适应观察到的磁盘vibrations在每个波段。使用我们的简单模型和假设的尘埃温度分布，我们估计在所有三个波段的光学深度。在233 GHz处的光学深度在$τ_{233} \sim 0.3$处达到峰值，这表明尘埃发射可能在光学上不足以使尘埃自散射有效。我们还发现，更高的灵敏度233 GHz的数据显示亚结构在磁盘上的第一次。子结构沿着长轴在恒星的两侧表现为更明亮的叶瓣。我们试图用一个简单的几何模型来拟合波瓣，但在233 GHz的数据中，它们是未解决的。我们建议圆盘可以张开1 mm，这样当倾斜观察时，沿长轴的尘埃柱比沿短轴的尘埃柱高。这些观测突出了从尘埃偏振观测研究磁盘结构的高灵敏度连续数据的强度。

英文摘要：

WL 17 is a young transition disk in the Ophiuchus L1688 molecular cloud complex. Even though WL 17 is among the brightest disks in L1688 and massive enough to expect dust self-scattering, it was undetected in polarization down to ALMA's instrument sensitivity limit. Such low polarization fractions could indicate unresolved polarization within the beam or optically thin dust emission. We test the latter case by combining the high sensitivity 233 GHz Stokes I data from the polarization observations with previous ALMA data at 345 GHz and 100 GHz. We use simple geometric shapes to fit the observed disk visibilities in each band. Using our simple models and assumed dust temperature profiles, we estimate the optical depth in all three bands. The optical depth at 233 GHz peaks at $τ_{233} \sim 0.3$, which suggests the dust emission may not be optically thick enough for dust self-scattering to be efficient. We also find the higher sensitivity 233 GHz data show substructure in the disk for the first time. The substructure appears as brighter lobes along the major axis, on either side of the star. We attempt to fit the lobes with a simple geometric model, but they are unresolved in the 233 GHz data. We propose that the disk may be flared at 1 mm such that there is a higher column of dust along the major axis than the minor axis when viewed at an inclination. These observations highlight the strength of high sensitivity continuum data from dust polarization observations to study disk structures.

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