解开年轻的混合盘HD 141569中的中平面气体和尘埃分布的秘密
Unlocking the secrets of the midplane gas and dust distribution in the young hybrid disc HD 141569
摘要：
HD 141569是一颗前主序星，它有一个独特的圆盘位于原行星盘和碎片盘之间，类似于较老的“混合”型圆盘。这项工作的目的是把质量和空间结构的光盘中平面的背景下的碎片，混合和原行星盘。我们用1.3mm连续谱的ALMA和$^{13}$ CO（2-1）观测了HD~141569。这是第一次检测和图像的光学薄气体发射从该光盘的中平面。在连续发射中，我们检测到一个未分辨的中心峰和一个在220 $\pm$ 10~au处的毫米发射环的组合，该环稍微位于散射光中发现的环之一的内部。环的最小尘埃质量为0.13 $\pm$ 0.02~M $_{\oplus}$，而在恒星位置未分辨的毫米峰主要是由于尘埃的最小值为1.2 $\pm$ 0.2~M $_{\oplus}$而产生的热辐射。$^{13}$ CO在恒星位置周围不对称分布，峰值在1.1”距离处，P.A. -33 $^\circ$。气体被检测到远至220 $\pm$ 10~au，径向间隔与mm环的径向间隔相同。假设光学薄发射和标准ISM丰度，我们使用我们的$^{13}$ CO数据来推导出（6.0 $\pm$ 0.9）$\times 10^{-4}~$ M $_\odot$盘中的气体质量。与已发表的$^{12}$ CO数据的比较表明，$^{12}$ CO是光学厚，解释了为什么基于$^{12}$ CO的估计低估了气体质量。
英文摘要：
HD141569 is a pre-main sequence star with a disc uniquely placed between protoplanetary and debris discs, similar to the older `hybrid' type discs. This work aims to place the mass and spatial structure of the disc midplane in the context of the debris, hybrid and protoplanetary discs. We observed HD~141569 with ALMA in 1.3~mm continuum and $^{13}$CO (2-1). This is the first detection and image of the optically thin gas emission from the midplane of this disc. In continuum emission, we detect a combination of an unresolved central peak and a ring of millimetre emission at 220$\pm$10~au, slightly interior to one of the rings discovered in scattered light. The minimum dust mass of the ring is 0.13$\pm$0.02~M$_{\oplus}$ while the unresolved millimetre peak at the stellar location is predominantly thermal emission due to a minimum of 1.2$\pm$0.2~M$_{\oplus}$ of dust. $^{13}$CO is distributed asymmetrically around the stellar position with a peak at 1.1" distance and a P.A. of -33$^\circ$. The gas is detected as far as 220$\pm$10~au, a radial separation the same as that of the mm ring. Assuming optically thin emission and standard ISM abundances, we use our $^{13}$CO data to derive the gas mass in the disc of (6.0$\pm$0.9) $\times 10^{-4}~$M$_\odot$. Comparison to published $^{12}$CO data shows that $^{12}$CO is optically thick, explaining why estimates based on $^{12}$CO underestimated the gas mass.
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