A Study of Volatile Molecules in the Inner Preplanetary Disks Around Herbig AeBe Stars

为了弄清物理结构、气体和尘埃的含量，以及围绕赫比格AeBe年轻发射线恒星周围尚不清楚的内星盘区域形成行星的可能性，PI已经开始了一项高分辨率红外（3-5mm）研究，研究预计存在的各种分子，如CO和h3 +。近红外光谱是一个具有挑战性的光谱区域，但这个光谱区域是探索CO以及对称碳氢化合物（例如ch4， c2h6, c2h2）和h3 +在热年轻恒星周围物质中的最佳选择。对于赫比格AeBe恒星，尚不清楚原始气体和尘埃是否能在靠近恒星的内部区域（1-50天文单位）保持足够长的时间，以发生行星形成。PI已经公布了几颗这样的恒星的结果，显示探测到CO， ch4和H3+（首次探测到太阳系外的H3+发射）。这项研究将使用基本的CO线（4.7mm）来测量这些恒星周围内盘的温度、柱密度和CO质量。对h3 +的观测可以对这些前主序星内部盘的化学过程和高能光处理的重要性提供更定量的理解。h3 +作为行星前盘中电离速率的直接探针是很重要的，在盘化学中也很重要，因为几乎所有的离子中性反应都是由这个分子初始化的。CO， ch4和h3 +的检测对于量化内盘的物理和化学演化以及约束气体耗散速率和行星形成的潜力具有重要意义。其次，h3 +被认为是寻找行星形成和/或行星盘演化证据的一种潜在方法，这将为理论学家提供一条约束行星盘和太阳系外行星形成的额外途径。

AST-0205881PI RettigTo clarify the physical structure, gas and dust content, as well as the potential for planetformation around the poorly understood inner circumstellar disk regions of Herbig AeBe young emission line stars, the PI has begun a high resolution infrared (3-5mm) study of various molecules such as CO and H 3+ that are expected to be present. The near-infrared is a challenging spectral region to work, but this spectral region is optimal to explore CO as well as the symmetric hydrocarbons (e.g. CH 4 , C 2 H 6 , C 2 H 2 ) and H 3+ in material around hot young stars. For Herbig AeBe stars, it is not clear that primordial gas and dust can remain sufficiently long in the inner regions (1-50 AU) close to the star for planet formation to occur. The PI has already presented results for several such stars showing the detection of CO, CH 4 , and H3+ (the first detection of H 3+ emission outside the Solar System ever made). This research will use fundamental CO lines (4.7mm) to measure temperatures, column densities, and mass of CO in the inner disks around these stars. Observations of H 3+ may provide a more quantitative understanding of the chemical processing and the importance of energetic photo-processing in inner disks of these pre-main sequence stars. H 3+ is important as a direct probe of the ionization rate in preplanetary disks and is important in disk chemistry as nearly all ion-neutral reactions are initialized by this molecule. The detection of CO, CH 4 , and H 3+ are important to quantify the physical and chemical evolution of the inner disk and also constrain the gas dissipation rate and potential for planetary formation. Secondly, H 3+ is shown as a potential method to search for evidence of planet formation and/or disk evolution that will provide theorists an additional avenue to constrain disk and extra-solar planet formation.