Molecules with ALMA at Planet-forming Scales (MAPS). VII. Substellar O/H and C/H and Superstellar C/O in Planet-feeding Gas-猫眼课题宝

DOI：

10.3847/1538-4365/ac1435

发表时间：

2021-09

期刊：

The Astrophysical Journal Supplement Series

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通讯作者：

中科院分区：

其他

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作者：

A. Bosman;Felipe Alarc'on;E. Bergin;Kecheng Zhang;Merel L. R. van’t Hoff;K. Öberg;V. Guzmán;C. Walsh;Y. Aikawa;S. Andrews;J. Bergner;A. Booth;G. Cataldi;L. Cleeves;I. Czekala;K. Furuya;Jane Huang;J. Ilee;C. Law;R. Le Gal;Yao Liu;F. Long;R. Loomis;F. Ménard;H. Nomura;C. Qi;K. Schwarz;R. Teague;T. Tsukagoshi;Yoshihide Yamato;D. Wilner

原行星盘中气体和尘埃的元素组成会影响在其上形成的行星的组成。我们使用ALMA at Planet-Foring Scales(MAP)数据来限制潜在行星形成位置上气体的元素组成。元素丰度是通过将DALI程序中具有不同C/O比和小颗粒丰度的特定源气体-颗粒热化学模型与由As209、HD 163296和MWC480的高分辨率观测得到的CO和C2H柱密度进行比较来推断的。提高的C/O比(∼2.0)，即使在CO冰线内，也是必要的，以匹配大部分卵石盘上推断的C2H柱密度。结合对这些系统中CO丰度的限制，这意味着气体中的O/H和C/H比都是恒星以下的4-10倍，O/H贫化20-50倍，导致高的C/O比。这就需要，即使在CO冰线内，大部分挥发性碳和氧仍然被困在中层的颗粒上。因此，在As209、HD 163296和MWC480盘的缝隙中积累气体的行星在达到卵石隔离质量后将获得非常少的碳和氧。在没有大气丰富事件的情况下，这些行星将具有强烈的恒星下O/H和C/H以及超恒星C/O大气组成。本文是《天体物理学杂志增刊》地图特刊的一部分。

The elemental composition of the gas and dust in a protoplanetary disk influences the compositions of the planets that form in it. We use the Molecules with ALMA at Planet-forming Scales (MAPS) data to constrain the elemental composition of the gas at the locations of potentially forming planets. The elemental abundances are inferred by comparing source-specific gas-grain thermochemical models with variable C/O ratios and small-grain abundances from the DALI code with CO and C2H column densities derived from the high-resolution observations of the disks of AS 209, HD 163296, and MWC 480. Elevated C/O ratios (∼2.0), even within the CO ice line, are necessary to match the inferred C2H column densities over most of the pebble disk. Combined with constraints on the CO abundances in these systems, this implies that both the O/H and C/H ratios in the gas are substellar by a factor of 4–10, with the O/H depleted by a factor of 20–50, resulting in the high C/O ratios. This necessitates that even within the CO ice line, most of the volatile carbon and oxygen is still trapped on grains in the midplane. Planets accreting gas in the gaps of the AS 209, HD 163296, and MWC 480 disks will thus acquire very little carbon and oxygen after reaching the pebble isolation mass. In the absence of atmosphere-enriching events, these planets would thus have a strongly substellar O/H and C/H and superstellar C/O atmospheric composition. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Molecules with ALMA at Planet-forming Scales (MAPS). VII. Substellar O/H and C/H and Superstellar C/O in Planet-feeding Gas

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