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

AST-0205881 PI Rettig为了弄清Herbig AeBe年轻发射线恒星的物理结构、气体和尘埃含量，以及在知之甚少的内部拱星盘区域周围形成行星的可能性，PI已经开始对各种分子进行高分辨率的红外（3- 5 mm）研究，如CO和H3+。近红外是一个具有挑战性的光谱区域，但这个光谱区域是探索CO以及热年轻恒星周围物质中的对称烃（例如CH 4，C2 H6，C2 H2）和H3+的最佳选择。对于Herbig AeBe恒星，我们还不清楚原始气体和尘埃是否能在靠近星星的内部区域（1-50 Au）停留足够长的时间以形成行星。 PI已经展示了几颗这样的恒星的结果，显示了CO，CH 4和H3+的探测（太阳系外首次探测到H3+的发射）。这项研究将使用基本的CO线（4.7毫米）来测量这些恒星周围内部圆盘中的温度，柱密度和CO质量。 对H3+的观测可以提供对这些前主序星内盘化学过程和高能光处理重要性的更定量的理解。H 3+是重要的，因为它是前行星盘电离率的直接探针，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种分子引发的。 CO、CH 4和H3+的检测对于量化内盘的物理和化学演化非常重要，也限制了气体耗散速率和行星形成的潜力。其次，H3+被证明是一种潜在的方法来寻找行星形成和/或盘演化的证据，这将为理论家提供一个额外的途径来限制盘和太阳系外行星的形成。

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.