Evolution of the radial and vertical distribution of protoplanetary disks from scattered-light observations

原行星盘是行星形成的地方。它们主要由分子气体组成，然而，从观测中获得气体分布（包括气体质量及其径向/垂直延伸）是具有挑战性的。因此，我们所掌握的关于行星在盘状结构中形成的大部分信息都来自占主导地位的盘状不透明尘埃。在观测上，我们可以分别通过光学/近红外散射光观测和干涉（亚）毫米观测获得微米级颗粒和卵石（mm/cm级颗粒）的分布。由于来自气体的空气动力阻力，鹅卵石受到径向漂移并以圆盘形式沉降到中间平面。因此，从观测中推断出的砾石的径向和垂直延伸并不能反映实际的气体盘分布。而小颗粒与气体耦合良好，其分布与气体分布接近。最近，VLT的SPHERE仪器提供了几个原行星盘的散射光图像，这是前所未有的。这个博士项目旨在将不同物理条件下原行星盘中气体和尘埃的演化模型联系起来，以控制它们的演化，并将结果与最先进的SPHERE观测结果进行比较。我是一个大型公认项目（DESTINYS）的国际合作项目的一部分，该项目针对不同年龄（从1到1000万年）的不同恒星形成区域的金牛座t星周围的85个原行星盘。有了这些数据的特权，在这个项目中，我们将研究在散射光中看到的原行星盘的径向和垂直分布及其演变，并将其与强大的望远镜（如ALMA）在毫米发射中观察到的结果联系起来，以便更好地理解支配圆盘演变的物理机制。有两种主要的机制被提出用于传输质量和角动量来驱动全球磁盘演化：湍流粘度和磁流体动力（MHD）磁盘风，它们都在气体磁盘大小的演化中留下了不同的印记：在湍流粘度的情况下，磁盘预计会随着时间的推移而膨胀，而在MHD风的情况下，情况正好相反。另一方面，原行星盘中小颗粒的垂直分布可以对盘内的垂直湍流提供约束，本项目将研究这种垂直湍流的潜在演化。了解驱动原行星盘演化的因素是理解行星如何在这些系统中形成以及与迄今为止观测到的大量系外行星联系起来的关键因素。

Protoplanetary disks are the sites of planet formation. They are mainly composed by molecular gas, however, accessing the gas distribution from observations (including gas mass and its radial/vertical extension) in disks is challenging. Therefore, most of the information that we have about planets forming in disks comes from the dust that dominates the disk opacity. Observationally, we can access the distribution of micron-sized particles and pebbles (mm/cm-sized particles) trough observations of scattered-light at optical/near infrared and interferometric (sub-) millimeter observations, respectively. Due to the aerodynamical drag from the gas, pebbles are subject to radial drift and settling to the midplane in disks. For this reason, the radial and vertical extension of pebbles inferred from observations do not trace the actual gas disk distribution. However, small grains are expected to be well coupled to the gas and their distribution is close to the gas distribution. Recently, the SPHERE instrument at VLT have provided unprecedented scattered-light images of several protoplanetary disks. This PhD project aims to connect models of gas and dust evolution in protoplanetary disks under different physical conditions that can rule their evolution and compare the results with state-of-the-art SPHERE observations. I am part of an international collaboration of a large accepted program (DESTINYS), which targets 85 protoplanetary disks around T-Tauri stars in different star forming regions with different age (from ~1 to 10 million years). With the privileged access to these data, in this project we will investigate the radial and vertical distribution in protoplanetary disks as seen in scattered light and its evolution, connect to what is observed at mm-emission from powerful telescopes, such as ALMA, in order to have a better understanding of the physical mechanisms that rule the evolution of disks.There are two leading mechanisms proposed for transporting mass and angular momentum that drive global disk evolution: turbulent viscosity and Magneto-hydrodynamical (MHD) disk winds, both of them leave different imprints on the evolution of the gas disk size: while the disk is expected to expand with time in the turbulent viscosity case, the opposite happens in the case of MHD winds. On the other hand, the vertical distribution of the small grains in protoplanetary disks can provide constrains on the vertical turbulence in the disks , and with this project we will study the potential evolution of such vertical turbulence. The knowledge of what drives the evolution of protoplanetary disk is a key element to understand how planets form in these systems and to link with the large population of exoplanets observed up to day.