HD 163296盘的空间分辨垂直温度梯度
A Spatially Resolved Vertical Temperature Gradient in the HD 163296 Disk
摘要：
我们分析敏感，亚弧秒分辨率ALMA科学验证观测的CO发射线在原行星盘主办的年轻，孤立的Ae星HD 163296。观测到的12 CO J=3-2发射线的空间形态在盘的长轴上是不对称的; 12 CO J=2-1线的特征是不太明显，但类似的不对称。~（12）CO及其主要同位素的J=2-1发射没有分辨的空间不对称性。我们将这种行为与盘中垂直温度梯度和分层分子结构的直接特征联系起来。这是证明使用玩具模型和更复杂的计算假设非局部热力学平衡（非LTE）条件。一个模型磁盘结构的开发，以再现独特的空间形态的12 CO J=3-2线，以及J=2-1的CO同位素的排放假设与星际介质的相对丰度一致。该模型盘结构具有τ =1的12 CO发射线的发射表面，其相对于盘中平面成大约15度的角度。此外，我们表明，这些数据的空间和光谱灵敏度可以区分模型，由于磁盘的垂直范围和其相关的径向压力梯度（在散装气体速度场的分数差约大于5%）的子开普勒气体速度。
英文摘要：
We analyze sensitive, sub-arcsecond resolution ALMA Science Verification observations of CO emission lines in the protoplanetary disk hosted by the young, isolated Ae star HD 163296. The observed spatial morphology of the 12CO J=3-2 emission line is asymmetric across the major axis of the disk; the 12CO J=2-1 line features a much less pronounced, but similar, asymmetry. The J=2-1 emission from 12CO and its main isotopologues have no resolved spatial asymmetry. We associate this behavior as the direct signature of a vertical temperature gradient and layered molecular structure in the disk. This is demonstrated using both toy models and more sophisticated calculations assuming non-local thermodynamic equilibrium (non LTE) conditions. A model disk structure is developed to reproduce both the distinctive spatial morphology of the 12CO J=3-2 line as well as the J=2-1 emission from the CO isotopologues assuming relative abundances consistent with the interstellar medium. This model disk structure has tau=1 emitting surfaces for the 12CO emission lines that make an angle of about 15 degrees with respect to the disk midplane. Furthermore, we show that the spatial and spectral sensitivity of these data can distinguish between models that have sub-Keplerian gas velocities due to the vertical extent of the disk and its associated radial pressure gradient (a fractional difference in the bulk gas velocity field of approximately greater than 5%).
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