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赫比格-哈羅天體高分辨觀測研究進展
Progress in Observational Studies with High Spatial Resolution on Herbig-Haro Objects
- doi：
- 摘要：
- 赫比格-哈羅天體(HH天體)包含了有關原恒星吸積和拋射過程的許多重要信息。HH天體高分辨觀測研究取得了一系列新進展：分辨出激波峰面、馬赫盤和輻射冷卻區；分辨出噴流節點的結構，發現它們大多是內工作面，而不是由Kelvin-Helmholtz不穩定性所產生的斜激波；發現噴流寬度隨到激發源距離的減小僅緩慢減小，對噴流的準直和加速模型提供了限制條件；HH天體在小尺度上尚有復雜的激發結構。對這些進展進行了評述。
- Abstract：
- Herbig-Haro objects and jets contain a lot of information concerning the accretion and ejection processes of protostars. The observational results fostered from the unprecedentedly high spatial resolution of Hubble Space Telescope (HST) are briefly reviewed. Bow shocks and Mach disks within the working surfaces of HH objects are fully resolved for the first time. The bright[S Ⅱ]knots on the working surfaces are found to be displaced from the bright Ha arcs located at the leading edges of bow shocks and the distances between them are identified as the "cooling distances", which in the HH 111V case is≈0.5"(230AU). The structures of the internal working surfaces within the jet bodies are also resolved. The three extended HH jets observed by HST, HH 34, HH 46/47, and HH 111, all display evidences of variations in jet velocity and direction, which supports the scenario that the knots within HH jets are the internal working surfaces driven by the time-variable eruptions of the exciting sources. Measurements of jet width at distance as close as 0.25"(35AU)to the sources reveal that the opening angles of jets decrease as the distances to the sources increase, which puts a strong constraint on models of jet collimation and acceleration. With HST observations of XZ Tau in two epochs we are witnessing the initial formation of a cooling zone in the front of an extremely young bubble with a dynamic age of≈23 yr. The discovery of complex excitation structures of a typical scale of 0.15"in HH 2A and 2H has important implications for the shock wave interpretation of HH objects.
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