Modelling the 3D high-resolution spectra of hot Jupiters

对热木星的 3D 高分辨率光谱进行建模

• 批准号: 2445269
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2445269
• 关键词: Modelling; 3D; resolution; spectra; hot

In the past ten years high resolution spectrum of exoplanet atmospheres became available from large ground based telescopes. Instruments such as NIRSPEC at the Keck telescope Hawaii or CRIRES at the Very Large Telescope Chile have been able to resolve individual spectral lines of both atoms such as sodium and molecules such as water and carbon monoxide. These observations not only allowed the detection and quantification of molecules but have provided the first direct measurement of an exoplanet atmospheric wind speed. With more than ten new instruments about to come to the sky in large telescope worldwide among them ESPRESSO at the Very Large Telescope and CARMENES at the Calar Alto have begun observing SPIRou at the Canada France Hawaii Telescope should start soon, high resolution spectra of exoplanet will be measured routinely with a high accuracy. Further ahead high resolution instruments such as METIS on the European Extremely Large Telescope will become our best chance to detect biosignatures in other worlds. Despite these exciting prospects, very small work has been done to interpret these observations. We learned from low resolution spectroscopywith space based telescopes such as Hubble or Spitzer or soon the James Webb Space Telescope that exoplanetary atmospheres are complex objects, particularly Hot Jupiters, the main targets of current observations. These planets have the size of Jupiter but orbit much close to their star than mercury. They are tidally locked, with a dayside heated to several thousands of degrees while their nightside never sees the star. Strong often supersonic winds transfer energy from the dayside to the nightside. Whereas the dayside can be hot enough to break molecules apart, the nightside shows signs of clouds made of rocky material such as silicates. High resolution spectroscopy observations are currently interpreted using one-dimensional atmospheric models. Whereas these can be used to atmospheric wind speeds and abundances from current observations they can be biased towards the wrong results. New more precise information such as recent ones by the ESPRESSO instrument can resolve the planetary limb during a transit, showing clear signs of 3D asymetries. For this project we will use a state of the art 3 dimensional global circulation model of hot exoplanets (the SPARC/MITgcm) to investigate the effects of a 3D thermal and wind structure on high-resolution observations. The dynamical model can predict complex thermal and chemical structure, cloud spatial distribution and wind patterns for a wide range of exoplanets. These outputs will be used by MCRT, a state of the art 3D monte carol radiative transfer code to calculate with a high precision the shape and position of the molecular lines observed with high resolution spectrocscopy. The student will determine the observational consequences of varying planetary parameters, such as equilibrium temperature, wind drag, gravity, cloud composition and re interpret current observations. We will also investigate what best 3D line shapes parametrization should be used when retrieving wind speed and abundances from the observations which should greatly enhanced the detectability of atmospheric species in these planets. Observation proposals in collaboration with local Oxford observes (such as Suzanne Aigrain in the astronomy departement) will be written to obtain open time on major observatories around the world following the insights gained from the modelling work

在过去的十年里，大型地面望远镜可以获得系外行星大气的高分辨率光谱。诸如夏威夷凯克望远镜上的NIRSPEC或智利甚大望远镜上的CRIRES等仪器已经能够分辨出钠等原子和水、一氧化碳等分子的单独光谱线。这些观测不仅允许对分子进行检测和量化，而且还提供了对系外行星大气风速的第一次直接测量。随着十多个新的仪器即将在世界各地的大型望远镜中出现，其中包括甚大望远镜的ESTERO和Calar Alto的CARMENES已经开始观察SPIRou，加拿大法国夏威夷望远镜应该很快开始，高分辨率的系外行星光谱将被高精度地定期测量。在未来，欧洲超大望远镜上的METIS等高分辨率仪器将成为我们探测其他世界生物特征的最佳机会。尽管这些令人兴奋的前景，非常小的工作已经做了解释这些意见。我们从哈勃或斯皮策等太空望远镜的低分辨率光谱学中了解到，系外行星大气是复杂的物体，特别是热彗星，目前观测的主要目标。这些行星有木星的大小，但轨道比水星更靠近它们的星星。它们被潮汐锁定，白昼被加热到几千度，而它们的黑夜永远看不到星星。强劲的超音速风将能量从昼侧传递到夜侧。白昼的温度足以将分子分解，而黑夜则显示出由硅酸盐等岩石材料构成的云的迹象。高分辨率光谱观测目前使用一维大气模型解释。虽然这些可以用于从当前观测的大气风速和丰度，但它们可能偏向于错误的结果。新的更精确的信息，如最近由ESTERO仪器提供的信息，可以在凌日期间解析行星边缘，显示出3D不对称的明显迹象。在这个项目中，我们将使用最先进的热系外行星的三维全球环流模型（the mixer/MITgcm）来研究3D热和风结构对高分辨率观测的影响。该动力学模型可以预测各种系外行星的复杂热和化学结构、云的空间分布和风的模式。这些输出将被MCRT使用，MCRT是一种最先进的3D蒙特卡洛辐射转移代码，用于高精度计算用高分辨率光谱仪观察到的分子线的形状和位置。学生将确定不同行星参数的观测结果，如平衡温度，风阻力，重力，云的组成和重新解释当前的观测。我们还将研究在从观测中检索风速和丰度时应使用什么最佳3D线形参数化，这将大大提高这些行星中大气物种的可探测性。与当地牛津观测员（如天文系的SuzanneAigrain）合作的观测建议将根据从建模工作中获得的见解编写，以获得世界各地主要天文台的开放时间