来自LkCa15的ALMA 3波段深度观测的尘埃陷阱高角分辨率证据
High angular resolution evidence of dust traps from deep ALMA Band 3 observations of LkCa15
AI总结：
本研究利用ALMA 3毫米波段高分辨率观测结合多波长数据，验证LkCa15原行星过渡盘的尘埃陷阱机制，确定了尘埃环特征、总质量范围及内盘辐射性质，并给出最优尘埃演化模型参数。
AI中文摘要：
尘埃陷阱是解释原行星盘中观测到的子结构的最有前景的机制。在本研究中，我们展示了针对LkCa15周围过渡盘的3毫米波段高角分辨率（约60毫角秒，对应9.4天文单位）、高灵敏度阿塔卡马大型毫米/亚毫米波阵列（ALMA）观测结果。这些新数据与此前在波长0.87、1.3毫米处的高分辨率观测相结合，使LkCa15成为检验尘埃捕获机制的理想实验室。我们发现三个环的宽度随频率线性减小，且光谱指数在环的位置呈现局部极小值，这与尘埃陷阱模型的预测一致。多波长建模证实，尘埃面密度和最大颗粒尺寸的峰值位于69和101天文单位处，在42天文单位处也存在疑似峰值。根据所选不透明度的不同，估算的总尘埃质量在13-250倍地球质量（M⊕）之间。内盘在3毫米波段表现出明亮且未被分辨的辐射，其1.3-3毫米波段的光谱指数α₁.₃₋₃mm为0.3±0.37，3毫米-3厘米波段的光谱指数α₃mm₋₃cm在-0.1到0.0之间。这些特征与电离喷流或盘风产生的自由-自由辐射相符。尘埃演化模型和辐射转移计算表明，黏度系数α=10⁻³、碎裂速度10米每秒以及DSHARP不透明度的组合能最好地匹配观测到的特征。
英文摘要：
Dust traps are the most promising mechanisms to explain the observed substructures in protoplanetary discs. In this work, we present high-angular resolution ($\sim$60 mas, 9.4 au) and high-sensitivity Atacama Large Millimetre/submillimetre Array (ALMA) observations at 3 mm of the transitional disc around LkCa15. The new data, combined with previous high-resolution observations at $λ=0.87,1.3$ mm, make LkCa15 an ideal laboratory for testing the dust trapping mechanism. We found that the width of the three rings decreases linearly with frequency, and the spectral indices show local minima at the locations of the rings, consistent with dust trap models. Multi-wavelength modelling confirms that the dust surface density and maximum grain size peak at 69 and 101 au, and suggestive peak at 42 au. The estimated total dust mass is between 13-250 M$_{\oplus}$, depending on the chosen opacity. The inner disc shows bright and unresolved emission at 3 mm, exhibiting a spectral index of $α_{1.3-3 \rm mm} = 0.3 \pm 0.37$, and $α_{\rm 3mm-3cm}$ ranging from $-0.1$ to $0.0$. These properties are consistent with free-free emission from an ionised jet or disc wind. Dust evolution models and radiative transfer calculations suggest that a viscosity coefficient of $α= 10^{-3}$, a fragmentation velocity of 10 m s$^{-1}$, and DSHARP opacities provide the best match to the observed properties.
