arXiv 1702.028442017-02-09astro-ph.SRastro-ph.EPastro-ph.GA

ALMA揭开了原行星系统HD 169142中的环和间隙：两颗巨型原行星的签名

ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets

D. Fedele, M. Carney, M. R. Hogerheijde, C. Walsh, A. Miotello, P. Klaassen, S. Bruderer, Th. Henning, E. F. vanDishoeck

备注：: Accepted for publication in A&A
发表信息：: A&A 600, A72 (2017)
DOI：: 10.1051/0004-6361/201629860

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摘要：

原行星系统HD 169142是最近通过直接成像发现潜在候选原行星的少数案例之一。为了研究原行星和盘本身之间的相互作用，需要对气体和尘埃表面密度结构进行观测。本文报道了HD 169142的1.3mm尘埃连续谱的ALMA新观测结果，观测到PDMATHABMMCO、PDMATHABMNCO和C-$^{18}$-O-$J=2-1$辐射，角分辨率为$\sim 0".18 - 0".28$（$\sim 20\,$ au $ - 33\,$ au）.尘埃连续谱的发射揭示了一个双环结构，内环在$0".17-0".28$（$\sim 20 - 35\,$ au）之间，外环在$0".48-0".64$（$\sim 56 - 83\,$ au）之间。内环的大小和位置与以前的近红外偏振观测结果非常一致，并且与大质量行星捕获的尘埃一致。在内部灰尘腔（$R \lesssim 20\,$ au）或灰尘间隙（$\sim 35 - 56\,$ au）内未检测到灰尘排放。相比之下，三个CO同位素的$J=2-1$线的通道图揭示了尘埃腔和尘埃间隙内气体的存在。气体盘的半径也远大于致密尘埃排放延伸到$\sim 1'.5$（$\sim 180\,$ au）。这种差异和急剧下降的连续发射在大半径点径向漂移的大尘埃颗粒（$>$ \micron -大小）。利用热化学圆盘程序\textsc{dali}，模拟了连续谱和CO同位素发射，定量测量了气体和尘埃的表面密度。由此产生的气体表面密度减少了一个因素$\sim 30-40$向内的灰尘间隙。气体和尘埃的分布暗示了多颗行星的存在，这些行星通过动态清除（尘埃腔和间隙）和尘埃捕获（双环尘埃分布）来塑造盘结构。

英文摘要：

The protoplanetary system HD 169142 is one of the few cases where a potential candidate protoplanet has been recently detected via direct imaging. To study the interaction between the protoplanet and the disk itself observations of the gas and dust surface density structure are needed. This paper reports new ALMA observations of the dust continuum at 1.3\,mm, $^{12}$CO, $^{13}$CO and C$^{18}$O $J=2-1$ emission from the system HD 169142 at angular resolution of $\sim 0".18 - 0".28$ ($\sim 20\,$au$ - 33\,$au). The dust continuum emission reveals a double-ring structure with an inner ring between $0".17-0".28$ ($\sim 20 - 35\,$au) and an outer ring between $0".48-0".64$ ($\sim 56 - 83\,$au). The size and position of the inner ring is in good agreement with previous polarimetric observations in the near-infrared and is consistent with dust trapping by a massive planet. No dust emission is detected inside the inner dust cavity ($R \lesssim 20\,$au) or within the dust gap ($\sim 35 - 56\,$au). In contrast, the channel maps of the $J=2-1$ line of the three CO isotopologues reveal the presence of gas inside the dust cavity and dust gap. The gaseous disk is also much larger than the compact dust emission extending to $\sim 1'.5$ ($\sim 180\,$au) in radius. This difference and the sharp drop of the continuum emission at large radii point to radial drift of large dust grains ($>$ \micron-size). Using the thermo-chemical disk code \textsc{dali}, the continuum and the CO isotopologues emission are modelled to quantitatively measure the gas and dust surface densities. The resulting gas surface density is reduced by a factor of $\sim 30-40$ inward of the dust gap. The gas and dust distribution hint at the presence of multiple planets shaping the disk structure via dynamical clearing (dust cavity and gap) and dust trapping (double ring dust distribution).

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