标题： HST-ULLYSES调查中年轻恒星周围H2的径向分布和激发 显示英文标题

标题： The Radial Distribution and Excitation of H2 around Young Stars in the HST-ULLYSES Survey

摘要： 气体在原行星盘内10天文单位内的空间分布和演化是估计行星形成初始条件的基础。 从内盘的光谱观测中得出的最重要的限制包括主要气相成分的径向分布，气体性质如何随着内盘尘埃演化而变化，以及高能恒星辐射如何影响化学丰度和激发条件。 我们介绍了作为$HST$/ULLYSES项目一部分获得的内盘分子氢（H$_{2}$）的径向分布、激发和演化情况的调查。 我们分析了ULLYSES DR5发布中的71个（63个吸积）前主序系统远紫外光谱，以表征H$_{2}$发射线、H$_{2}$解离连续发射以及主要光化学/盘演化驱动的紫外发射（Ly$\alpha$，紫外连续谱和C IV）。 我们利用H$_{2}$发射线的宽度表明，大多数荧光H$_{2}$主要产生于母恒星0.1 - 1.4天文单位范围内，并显示平均发射半径与吸积光度和尘埃盘质量之间的正相关关系。 我们发现H$_{2}$解离辐射与吸积主导的Ly$\alpha$光度以及内盘尘埃清除之间存在强相关性，描绘出一幅画面，即内3 au处的水分子在内盘的不透明度随时间下降时，受到强烈的Ly$\alpha$辐射的作用并发生解离。 显示英文摘要

摘要： The spatial distribution and evolution of gas in the inner 10 au of protoplanetary disks form the basis for estimating the initial conditions of planet formation. Among the most important constraints derived from spectroscopic observations of the inner disk are the radial distributions of the major gas phase constituents, how the properties of the gas change with inner disk dust evolution, and how chemical abundances and excitation conditions are influenced by the high-energy radiation from the central star. We present a survey of the radial distribution, excitation, and evolution of inner disk molecular hydrogen (H$_{2}$) obtained as part of the $HST$/ULLYSES program. We analyze far-ultraviolet spectroscopy of 71 (63 accreting) pre-main sequence systems in the ULLYSES DR5 release to characterize the H$_{2}$ emission lines, H$_{2}$ dissociation continuum emission, and major photochemical/disk evolution driving UV emissions (Ly$\alpha$, UV continuum, and C IV). We use the widths of the H$_{2}$ emission lines to show that most fluorescent H$_{2}$ arises between 0.1 - 1.4 au from the parent star, and show positive correlations of the average emitting radius with the accretion luminosity and with the dust disk mass. We find a strong correlation between H$_{2}$ dissociation emission and both the accretion-dominated Ly$\alpha$ luminosity and the inner disk dust clearing, painting a picture where water molecules in the inner 3 au are exposed to and dissociated by strong Ly$\alpha$ emission as the opacity of the inner disk declines with time.