Elemental abundance retrievals in planet-forming disks: links to embedded protoplanets

在21世纪20年代，系外行星领域将越来越多地转向行星组成研究。其中一个关键方面是将行星元素丰度与其在圆盘中的形成历史联系起来。形成模型需要测量行星形成盘中的气相元素丰度比（例如，C/O），以可靠地预测行星的化学成分。随着人们对行星形成的化学诊断、生物标志物的兴趣日益增长，以及系外行星大气检索数据和方法的快速进展，这越来越及时。到目前为止，在行星形成盘中，元素丰度的测量是在非常粗糙的空间分辨率下完成的（平均丰度比超过10 -100 au尺度），并且通过一个繁琐的过程来运行少数（最大100阶）复杂的模型，基本上是手工拟合，从（亚）毫米望远镜（APEX， IRAM， ALMA等）获得各种连续体和线数据。这意味着，与系外行星研究的最新水平相比，我们对方法中的简并性、最佳数据采集以及盘中衍生丰度的真正不确定性的理解还很差。我们现在正在识别磁盘气体和尘埃中的空隙，并将嵌入的原行星与它们联系起来，信心日益增强。ALMA使我们能够在~10au尺度上获得前所未有的化学成分数据。将我们的圆盘平均丰度测量技术应用于小尺度，研究特定原行星附近的气体，以及测试日益复杂但约束不足的圆盘元素组成模型，正迅速变得至关重要。这些进展将是解开即将到来的JWST和Ariel系外行星组成数据洪流的关键。在这个项目中，你将有机会利用新的数据和开发方法来推进磁盘和行星组成联系的前沿。

In the 2020s, the exoplanet field will move increasingly towards planetary composition studies. One of the key aspects is to link planetary elemental abundances to their formation history in disks. Measurements of gas-phase elemental abundance ratios (e.g., C/O) in planet-forming disks are needed for formation models to reliably predict planetary chemical compositions. This is increasingly timely, with the growing interest in chemical diagnostics of planet formation, biomarkers, and rapid progress in exoplanet atmospheric retrieval data and methods. In planet-forming disks so far, elemental abundance measurements have been done with very coarse spatial resolution (average abundance ratios over 10s-100s of au scales) and through a cumbersome process of running a handful (maximum of order 100) complicated models to be fitted, essentially by hand, to a variety of continuum and line data from (sub-)millimetre telescopes (APEX, IRAM, ALMA, etc.). This means our understanding of degeneracies in the methods, optimal data acquisition, and true uncertainties in the derived abundances in disks is poor compared to the state of the art in exoplanet studies. We are now identifying gaps in disk gas and dust, and associating embedded protoplanets with them, with growing confidence. ALMA is allowing us to obtain unprecedented chemical composition data on ~10au scales. It is quickly becoming essential to adapt our disk-averaged abundance measurement techniques for small scales, to study gas in the vicinity of specific protoplanets and to test increasingly complex but poorly constrained disk elemental composition models. These advances will be key to unlocking the impending flood of JWST and Ariel exoplanet composition data. In this project, you will have an opportunity to exploit new data and develop methods to advance the cutting edge of disk and planet composition links.