DG Tau喷流的亚弧秒[ FeII ]光谱成像：周期性气泡和尘埃盘风？
Sub-arcsecond [FeII] spectro-imaging of the DG Tau jet: Periodic bubbles and a dusty disk wind?
摘要：
本文介绍了在[Fe Ⅱ]谱线上用SINFONI/VLT观测金牛座DG喷流的结果，其角分辨率为0.15”，光谱分辨率为R=3000。我们观察到一个洋葱状的速度结构[铁]在蓝移射流，类似于光学线路中观察到的。~-200 km/s的高速气体在4度的半开角内准直，而~-100 km/s的中速气体在半开角为14度的圆锥内准直。在蓝色射流中检测到两个新的轴向射流结，以及一个更远的气泡和相应的反气泡。周期性的纽结抛射时间尺度被向下修正为2.5年。红移喷流仅在距离恒星0.7”以外被探测到，从而修正了对盘表面密度的限制。通过与[OI]数据的比较，我们推断铁的损耗在高速下为3倍，在低于-100 km/s的速度下为10倍。蓝移叶的中高速分量的质量通量约为1.6+-0.8x10 ^-8 Msun/yr，相当于盘吸积速率的0.02-0.2。DG Tau射流中的中速锥形[Fe II]流太快且太窄，无法追踪来自磁盘大气的光蒸发物质。它的运动学和准直都不能被X风重现，“锥形磁层风”也不能。DG Tau中速分量中的Fe气相耗尽水平也排除了从高速光束侧向喷射的恒星风和茧。一个准稳定的离心MHD磁盘风喷射超过0.25-1.5 AU和/或情节磁塔空腔从磁盘推出出现作为最合理的起源中的DG头喷流的中速分量。同样的盘风模型也可以解释高速流的性质，尽管不能排除磁层风和/或恒星风的替代起源。
英文摘要：
We present SINFONI/VLT observations of the DG Tauri jet in the [FeII] lines with 0.15" angular resolution and R=3000 spectral resolution. We observe an onion-like velocity structure in [FeII] in the blueshifted jet, similar to that observed in optical lines. High-velocity gas at ~-200 km/s is collimated inside a half-opening angle of 4 degrees and medium-velocity gas at ~-100 km/s in a cone with an half-opening angle 14 degrees. Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. The redshifted jet is detected only beyond 0.7" from the star, yielding revised constraints on the disk surface density. From comparison to [OI] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km/s. The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are ~1.6+-0.8x10^-8 Msun/yr, representing 0.02-0.2 of the disk accretion rate. The medium-velocity conical [FeII] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25-1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.
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