Water Transport and Dispersal of Gas in Protoplanetary Disks

原行星盘中的水传输和气体扩散

• 批准号: 0908479
• 负责人: Paul Feldman
• 金额: $ 40万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0908479&HistoricalAwards=false
• 关键词: Water; Transport; Dispersal; Gas; Protoplanetary

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Through this award, Dr. Pascucci, along with students and collaborators, will complete an on-going ground-based campaign to spectrally resolve bright gas emission lines detected with the Spitzer Space Telescope toward many protoplanetary disks. These observations, combined with the space-based data, will address two fundamental questions related to the formation of giant and terrestrial planets: (1) When and through which mechanisms do gas disks disperse? (2) Can water vapor remain long in the disk to affect the water abundance of terrestrial planets? Specifically, Dr. Pascucci and her collaborators will:(1) Investigate how to use the emission line from ionized neon at 12.81 microns to trace dissipating gas disks. Disk models predict that this emission is a sensitive tracer of small gas masses in the terrestrial and giant planet forming region of disks. The Spitzer Space Telescope has detected spatially and spectrally unresolved neon emission lines toward many young disks. Dr. Pascucci and her collaborators will use ground-based telescopes to spectrally resolve bright neon lines from 30 prototoplanetary disks. By measuring the widths, peak velocities, and modeling the line profiles, they will separate the emission originating in a disk from that in a jet/outflow and measure the disk radii contributing to the spectal flux, and reveal if X-rays or ultraviolet photons are the major ionization source for neon atoms. This can clarify the role of photoevaporation in dispersing gas disks and guide the use of the numerous spectrally unresolved neon lines in measuring the timescale over which gas disperses.(2) Map out the distribution and evolution of water in protoplanetary disks. A key yet unanswered question is how Earth acquired its water. A new emerging scenario suggests that this happened relatively early, before Earth was fully formed, by accretion of hydrated silicates migrating inward from the outer asteroid belt. Models of the transport of water in an evolving protoplanetary disk identify robust trends in the evolution of water vapor. Dr. Pascucci and her collaborators will acquire the datasets to test these models. In particular, they will obtain high-resolution L-band spectra of disks in different evolutionary stages that have mid-infrared water lines detected with Spitzer. They will model the line profiles using various codes to: a) estimate the properties of the gas traced by the L-band water lines; and b) investigate if water emission lines are correlated with the disk evolutionary stage as proposed by disk models. Finally, they will work on the combined interpretation of L-band, mid-infrared and far-infrared water lines that they will obtain from their approved Herschel Key program to map out the distribution and evolution of water in protoplanetary disks. The proposed work is an essential complement to current and upcoming space-based observations, necessary to fully understand the evolution of gas in disks and the implications of this evolution on the formation of giant and terrestrial planets. This research program will form the basis for a PhD thesis for a Johns Hopkins University graduate student and offer small- and large- scale projects for undergraduate students interested in planet formation studies. These activities will train students in using state-of-the-art ground- and space-based facilities and in addressing some of the most fundamental questions in planet formation studies.

该奖项由《2009 年美国复苏与再投资法案》（公法 111-5）资助。通过该奖项，Pascucci 博士将与学生和合作者一起完成一项正在进行的地面活动，以光谱方式解析斯皮策太空望远镜检测到的许多原行星盘的明亮气体发射线。这些观测结果与天基数据相结合，将解决与巨行星和类地行星形成相关的两个基本问题：（1）气盘何时以及通过何种机制分散？ （2）水蒸气在圆盘中停留时间长会影响类地行星的水丰度吗？具体来说，Pascucci 博士和她的合作者将：(1) 研究如何使用 12.81 微米电离氖的发射线来追踪耗散气体盘。圆盘模型预测，这种排放是圆盘形成区域的类地行星和巨行星形成区域中小气体质量的敏感示踪剂。斯皮策太空望远镜探测到了许多年轻圆盘的空间和光谱上未解析的氖发射线。帕斯库奇博士和她的合作者将使用地面望远镜对来自 30 个原行星盘的明亮霓虹灯线进行光谱解析。通过测量宽度、峰值速度和对线轮廓进行建模，他们将把源自圆盘的发射与射流/流出的发射分开，并测量对光谱通量有贡献的圆盘半径，并揭示X射线或紫外光子是否是氖原子的主要电离源。 这可以阐明光蒸发在分散气体盘中的作用，并指导使用大量光谱上未解析的氖线来测量气体分散的时间尺度。(2)绘制出原行星盘中水的分布和演化。一个尚未解答的关键问题是地球如何获得水。一种新出现的情况表明，这种情况发生得相对较早，在地球完全形成之前，是由从小行星带外层向内迁移的水合硅酸盐的积聚造成的。不断演化的原行星盘中的水传输模型确定了水蒸气演化的强劲趋势。帕斯库奇博士和她的合作者将获取数据集来测试这些模型。特别是，他们将获得不同演化阶段的圆盘的高分辨率 L 波段光谱，这些圆盘具有用斯皮策探测到的中红外水线。他们将使用各种代码对线路剖面进行建模，以： a) 估计 L 波段水线追踪的气体特性； b) 研究水排放线是否与圆盘模型提出的圆盘演化阶段相关。最后，他们将致力于对 L 波段、中红外和远红外水线的综合解释，这些水线是从他们批准的赫歇尔密钥计划中获得的，以绘制原行星盘中水的分布和演化。拟议的工作是对当前和即将进行的天基观测的重要补充，对于充分了解圆盘中气体的演化以及这种演化对巨行星和类地行星形成的影响是必要的。该研究项目将为约翰霍普金斯大学研究生的博士论文奠定基础，并为对行星形成研究感兴趣的本科生提供小型和大型项目。这些活动将训练学生使用最先进的地面和天基设施，并解决行星形成研究中的一些最基本的问题。