RUI: Optical and Infrared Observations of Herbig-Haro Objects

将对赫比格-哈罗天体（恒星）的激波结构进行全面的光学和红外观测。这项研究的一个基本目的是了解来自年轻恒星物体的高速喷流的动力学，以及高速物质向周围分子介质传递动量和能量的方式。基本假设是，分子氢发射是由高速射流材料夹带的低速激波和/或穿透分子介质的射流工作表面弓形激波的扩展翼产生的。在这两种情况下，氢分子都被加速到介于高温赫比格-哈罗激波和更广泛的一氧化碳（C0）外流中存在动量耦合的光学发射线之间的中间速度。一个尚未解决的主要问题涉及光学冲击和产生氢分子发射的冲击之间的关系，前者涉及的冲击速度大于约50公里/秒，后者需要的冲击速度小于约30公里/秒。在许多情况下，光学激波似乎与分子激波在空间上是一致的，但光学和分子氢的发射不太可能是由一个共同的激波后气体产生的。选定的赫比格-哈罗天体将在氢α和SII的光学发射谱线区域以及氢分子和FeII的红外谱线区域获得高空间分辨率图像。FeII /（分子氢）谱线强度比可以推断气相重元素在颗粒上的耗损，从而确定被冲击的气体是射流气体还是环境介质气体。SII /（氢α）比是气体激发的一个度量，一般来说，在SII /（氢α）强度比最大的结构中或附近，分子氢的发射预计是最强的。对于两个被光学遮挡的赫比格-哈罗喷流，FeII的1.64微米波长线将用于追踪激波的“光学”成分。在光谱的光学部分和红外部分获得的高分辨率光谱数据将用于检查冲击波后气体的径向速度和速度色散。这些数据将解决低激发光发射是否与氢分子的发射来自相同的冲击波后气体的问题。空间分辨光谱也将允许区分磁前驱体和弓形激波模型。在恒星形成的更大背景下，对即将进行的观测结果的解释将对年轻恒星物体的双极分子外流的起源问题提供相当大的见解。最近的理论模型表明，高速射流为C0发射中更广泛的低速分子流出提供了驱动动力。对低激发赫比格-哈罗物体和在高低速流边界发现的氢分子发射的研究可以用来估计能量和动量向周围气体转移的效率。

9417209 Schwartz A comprehensive program of optical and infrared observations of the shock wave structure of Herbig-Haro objects (stars) will be carried out. A basic aim of the study is to understand the dynamics of high-velocity jets from young stellar objects and the manner in which the high velocity material transfers momentum and energy to the ambient molecular medium. The fundamental hypothesis is that molecular hydrogen emission is produced by low-velocity shocks via entrainment by high-velocity jet material and/or in the extended wings of the bow shocks in the working surface of a jet penetrating into the molecular medium. In both cases, molecular hydrogen is accelerated to intermediate velocities between those found for optical emission lines in the high-temperature Herbig-Haro shocks and in the more widespread carbon monoxide (C0) outflows in which there is momentum coupling. A major unresolved issue concerns the relation of the optical shocks, which involve shock velocities greater than about 50 km per second, and the shocks which produce molecular hydrogen emission which would require shock velocities less than about 30 km per second. In many cases, the optical shocks appear to be coincident spatially with the molecular shocks, yet it is unlikely that both the optical and the molecular hydrogen emission arise from a common postshock gas. High spatial resolution images of selected Herbig-Haro objects will be obtained in area of the spectrum of the optical emission lines of Hydrogen alpha and SII and in the infrared lines of molecular hydrogen and FeII . The FeII /(molecular hydrogen) line intensity ratio can be used to infer the depletion of gas phase heavy elements onto grains, and thus to determine whether the gas being shocked is jet gas or ambient medium gas. The SII /(Hydrogen alpha) ratio is a measure of excitation of the gas, and in general the emission from molecular hydrogen is expected to be strongest in or near structures with the largest SII /(Hydrogen alpha) intensity ratio. For two optically obscured Herbig-Haro outflows, the 1.64 micron wavelength line of FeII will be used to trace the "optical" component of the shocks. The acquisition of high resolution spectral data in both the optical and infrared portions of the spectrum will be used to examine the radial velocities and velocity dispersions of the postshock gas. The data should resolve the question of whether the low-excitation optical emission arises from the same postshock gas as the emission from molecular hydrogen. The spatially-resolved spectra will also permit a discrimination between magnetic precursor and bow shock models. In the larger context of star formation, the interpretations of the observations to be carried out will lend considerable insight into the question of the origin of bipolar molecular outflows from young stellar objects. Recent theoretical models suggest that high-velocity jets provide the driving power for the more widespread low-velocity molecular outflows seen in C0 emission. The study of low-excitation Herbig-Haro objects and emission from molecular hydrogen found at the boundaries of the high and low-velocity flows can be used to estimate the efficiency with which energy and momentum are transferred to the ambient gas.