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arXiv 2109.06217astro-ph.GAastro-ph.EPastro-ph.SR
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行星形成尺度上具有ALMA的分子(MAPS)IV:分子的发射面和垂直分布

Molecules with ALMA at Planet-forming Scales (MAPS) IV: Emission Surfaces and Vertical Distribution of Molecules

Charles J. Law, Richard Teague, Ryan A. Loomis, Jaehan Bae, Karin I. Öberg, Ian Czekala, Sean M. Andrews, Yuri Aikawa, Felipe Alarcón, Edwin A. Bergin, Jennifer… 展开作者

Charles J. Law, Richard Teague, Ryan A. Loomis, Jaehan Bae, Karin I. Öberg, Ian Czekala, Sean M. Andrews, Yuri Aikawa, Felipe Alarcón, Edwin A. Bergin, Jennifer B. Bergner, Alice S. Booth, Arthur D. Bosman, Jenny K. Calahan, Gianni Cataldi, L. Ilsedore Cleeves, Kenji Furuya, Viviana V. Guzmán, Jane Huang, John D. Ilee, Romane Le Gal, Yao Liu, Feng Long, François Ménard, Hideko Nomura, Laura M. Pérez, Chunhua Qi, Kamber R. Schwarz, Daniela Soto, Takashi Tsukagoshi, Yoshihide Yamato, Merel L. R. van't Hoff, Catherine Walsh, David J. Wilner, Ke Zhang

摘要:

行星形成尺度下的分子与ALMA(MAPS)大型计划提供了一个独特的机会来研究IM Lup,GM Aur,AS 209,HD 163296和MWC 480周围原行星盘中气体,化学和温度的垂直分布。通过利用分子线发射相对于盘主轴的不对称性,我们推断出中平面以上的发射高度($z$)作为半径($r$)的函数。利用这种方法,我们测量了一套CO同位素,HCN和C $_2$ H的发射表面。我们发现,$^{12}$ CO排放的痕迹与$z/r > 0.3$最高的地区,而排放较少丰富的$^{13}$ CO和C $^{18}$ O探针更深的磁盘在海拔高度的$z/r \lesssim 0.2$。C $_2$ H和HCN具有较低的不透明度和SNR,使得表面拟合更加困难,并且只能在AS 209、HD 163296和MWC 480中用$z/r \lesssim 0.1$可靠地约束,即,相对靠近行星形成中平面。我们确定峰值亮度温度的光学厚CO同位素,并使用这些跟踪二维磁盘温度结构。几个CO的温度分布和排放表面显示在温度或垂直高度,其中一些是与线和/或连续排放的间隙和环的下降。这些子结构可能是由于CO柱密度,气体表面密度,或气体温度的局部变化,详细的热化学模型是必要的,以更好地约束其起源和相关的化学成分升高磁盘层与行星形成的材料在磁盘中平面。本文是《天体物理学杂志增刊》MAPS特刊的一部分。

英文摘要:

The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a unique opportunity to study the vertical distribution of gas, chemistry, and temperature in the protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. By using the asymmetry of molecular line emission relative to the disk major axis, we infer the emission height ($z$) above the midplane as a function of radius ($r$). Using this method, we measure emitting surfaces for a suite of CO isotopologues, HCN, and C$_2$H. We find that $^{12}$CO emission traces the most elevated regions with $z/r > 0.3$, while emission from the less abundant $^{13}$CO and C$^{18}$O probes deeper into the disk at altitudes of $z/r \lesssim 0.2$. C$_2$H and HCN have lower opacities and SNRs, making surface fitting more difficult, and could only be reliably constrained in AS 209, HD 163296, and MWC 480, with $z/r \lesssim 0.1$, i.e., relatively close to the planet-forming midplanes. We determine peak brightness temperatures of the optically thick CO isotopologues and use these to trace 2D disk temperature structures. Several CO temperature profiles and emission surfaces show dips in temperature or vertical height, some of which are associated with gaps and rings in line and/or continuum emission. These substructures may be due to local changes in CO column density, gas surface density, or gas temperatures, and detailed thermo-chemical models are necessary to better constrain their origins and relate the chemical compositions of elevated disk layers with those of planet-forming material in disk midplanes. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

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