The role of large molecules in space

大的碳质分子，如多环芳烃（PAHs）和富勒烯，在星周和星际环境的物理和化学中起着关键作用。 多环芳烃在几乎所有的银河系和河外中红外观测中都留下了强烈而清晰的光谱指纹。它们的观测特征的变化取决于它们所处环境的物理条件，因此多环芳烃是研究宇宙的潜在有力工具。然而，关于天体物理PAH人群的细节和这些变化的根本原因仍然不清楚，限制了他们的诊断能力。我开发了一种方法，定量相关的物理输入参数（如辐射场的强度）的光谱特征，从美国宇航局艾姆斯PAH红外光谱数据库的许多物种的属性的基础上。我建议将这种方法应用于PAH光谱的对象，其环境是很好的特点;调查的起源众多的弱PAH功能;并实现带轮廓不对称的模型中以一致的方式。 最近，我们发现了已知存在于太空中的最大分子-富勒烯物种C60和C70。就像多环芳烃一样，富勒烯被证明是广泛存在的，并且在它们的观测特征中显示出微妙的变化。我建议开展几个观测项目，研究富勒烯的激发机制，它们的形成机制，演化，丰度和分布，以及它们与其他灭绝特征的关系，特别是弥漫性星际带（DIBs）。 拟议的方案将使人们更好地了解和理解空间大分子的形成、演变和分布，以及它们在星际和星周环境的物理和化学中的具体作用。

A key role in the physics and chemistry of circumstellar and interstellar environments is played by large carbonaceous molecules such as polycyclic aromatic hydrocarbons (PAHs) and fullerenes. PAHs leave their strong and clear spectral fingerprint in almost all galactic and extragalactic mid-infrared observations. Variations in their observational characteristics depend on the physical conditions of the environment in which they reside, and thus PAHs are potentially powerful tools to study the Universe. However, specifics about the astrophysical PAH population and the underlying causes for these variations remain unclear, limiting their diagnostic power. I developed a method that quantitatively relates physical input parameters (e.g. strength of the radiation field) to spectral features, based on properties of numerous species from the NASA Ames PAH infrared spectroscopic database. I propose to apply this method to the PAH spectra of objects whose environment is well characterized; to investigate the origin of the numerous weak PAH features; and to implement band profile asymmetries in the model in a consistent way. Recently, we detected the largest molecules known to exist in space -- the fullerene species C60 and C70. Just like PAHs, fullerenes turn out to be widespread, and to show subtle variations in their observational characteristics. I propose to carry out several observational projects to study the excitation mechanism of fullerenes, their formation mechanism, evolution, abundance and distribution, and their relation to other extinction features, and in particular the Diffuse Interstellar Bands (DIBs). The proposed program will lead to a better knowledge and understanding of the formation, evolution and distribution of large molecules in space and their specific role in the physics and chemistry of interstellar and circumstellar environments.