本研究利用 ALMA 数据对 HD 163296 原行星盘中原子碳 [CI] 发射进行径向与垂直结构分析，并与 CO 发射比较，发现二者径向共位但垂直高度不同，CO 位于更高处，可能由盘上层混合或紫外穿透所致。
摘要：
在原行星盘中，原子碳预计起源于盘表面的光致离解区（PDR），在该区域，一氧化碳（CO）被来自恒星或外部星际辐射场的紫外光子所离解。尽管原子碳已在多个原行星盘中被探测到，但对其空间分辨观测仍然缺乏。针对 HD 163296 原行星盘，我们旨在获取 [CI]${^3}{P_1} - {^3}{P_0}$ 谱线发射的径向和垂直结构，并将该示踪物与光学厚谱线发射 $^{12}$CO $J=2-1$ 进行首次直接比较。我们使用了档案中的 ALMA 数据用于 [CI]${^3}{P_1} - {^3}{P_0}$，以及先前发表的 HD 163296 中 ${^{12}}$CO $J=2-1$ 数据。通过 disksurf 软件，我们提取了垂直结构，同时直接从成像中获得了径向轮廓。我们采用了全新的 DALI 建模，以与数据进行直接比较。我们发现这些示踪物在径向上共位，但在垂直方向上不共位，其中 $^{12}$CO $J=2-1$ 发射平均位于更高的高度，这与同一盘中其他示踪物的情况一致。由于发射垂直高度的这种差异，光学厚的 $^{12}$CO $J=2-1$ 发射线似乎示踪了最高的高度，尽管 [CI] 在盘中的预期形成机制并非如此。后一种现象可能归因于盘上层的高效混合，或紫外光子穿透深度超出我们的预期。
英文摘要：
In protoplanetary disks, atomic carbon is expected to originate from the PDR at the disk surface where CO is dissociated by UV photons coming from the stellar, or external interstellar, radiation field. Even though atomic carbon has been detected in several protoplanetary disks, there is a lack of spatially resolved observations of it. For HD 163296 protoplanetary disk, we aim to obtain both radial and vertical structure of [CI]$={^3}{P_1} - {^3}{P_0}$ line emission and perform the first direct comparison of this tracer with optically thick line emission $^{12}$CO $J=2-1$. We used archival ALMA data for [CI]$={^3}{P_1} - {^3}{P_0}$ and previously published ${^{12}}$ CO $J=2-1$ data in HD 163296. Through the software of disksurf we extracted the vertical structure, meanwhile radial profiles were obtained directly from imaging. Brand new DALI modelling was employed to perform direct comparison to the data. We found that these tracers are collocated radially but not vertically, where $^{12}$CO $J=2-1$ emission is, on average, located at higher altitudes, as it is also the case for other tracers in the same disk. Due to this difference in vertical height of the emission, the optically thick $^{12}$CO $J=2-1$ emission line appears to trace the highest altitudes, despite the expected formation mechanism of [CI] in the disk. The latter phenomena may be due to efficient mixing of the upper layers of the disk, or UV photons penetrating deeper than we expected.
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Ring Spacing from a Fourth-Order Radial Feedback Green Function in a Keplerian Accretion Disk
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Institute of Science and Technology for Deep Space Exploration, Nanjing University（南京大学深空探测科学与技术研究院）
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