EVIDENCE FOR DISK PHOTOEVAPORATION DRIVEN BY THE CENTRAL STAR
EVIDENCE FOR DISK PHOTOEVAPORATION DRIVEN BY THE CENTRAL STAR
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DOI：
10.1088/0004-637x/702/1/724
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发表时间：
2009-08
期刊：
影响因子：
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通讯作者：
I. Pascucci;M. Sterzik
中科院分区：
文献类型：
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作者：
I. Pascucci;M. Sterzik
孤立的原行星盘的寿命被认为是由恒星高能光子驱动的粘性吸积和光蒸发共同决定的。年轻的类太阳恒星中磁层吸积的观测证据是强有力的。在这里，我们报道了由中央恒星驱动的盘状光蒸发的第一个观测证据。我们在Melipal/∼上使用VISIR获得了7个恒星周盘的[Ne II]12.81μm谱线的高分辨率(R VLT30,000)光谱。我们发现，样品中的三个过渡盘都有与恒星极紫外线(EUV)光子驱动的光蒸发流相一致的[Ne II]线型。∼6公里S−1从TW Hya几乎面对面的圆盘蓝移，显然与静止圆盘大气的发射不一致，并令人信服地指出存在光蒸发风。我们没有从经典的光学厚度(非跃迁)圆盘的样本中探测到任何接近恒星速度的[Ne II]线。我们的结论是，在这些演化程度较低的系统中，大部分光谱上未分辨的[Ne II]发射来自喷流/外流，而不是来自圆盘。[Ne II]探测和未探测的模式表明，EUV驱动的光蒸发只是在盘状演化的较晚阶段才开始。
The lifetime of isolated protoplanetary disks is thought to be set by the combination of viscous accretion and photoevaporation driven by stellar high-energy photons. Observational evidence for magnetospheric accretion in young Sun-like stars is robust. Here we report the first observational evidence for disk photoevaporation driven by the central star. We acquired high-resolution (R∼ 30,000) spectra of the [Ne ii] 12.81 μm line from seven circumstellar disks using VISIR on Melipal/VLT. We show that the three transition disks in the sample all have [Ne ii] line profiles consistent with those predicted by a photoevaporative flow driven by stellar extreme-ultraviolet (EUV) photons. The ∼6 km s−1 blueshift of the line from the almost face-on disk of TW Hya is clearly inconsistent with emission from a static disk atmosphere and convincingly points to the presence of a photoevaporative wind. We do not detect any [Ne ii] line close to the stellar velocity from the sample of classical optically thick (nontransition) disks. We conclude that most of the spectrally unresolved [Ne ii] emission in these less-evolved systems arises from jets/outflows rather than from the disk. The pattern of the [Ne ii] detections and nondetections suggests that EUV-driven photoevaporation starts only at a later stage in the disk evolution.