DIGIT survey of far-infrared lines from protoplanetary discs: II. CO
DIGIT survey of far-infrared lines from protoplanetary discs: II. CO
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原行星盘远红外线的数字调查：II。
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发表时间：
2013
期刊：
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通讯作者：
The Digit Team
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作者：
G. Meeus;C. Salyk;S. Bruderer;D. Fedele;K. Maaskant;N. Evans;E. Dishoeck;B. Montesinos;G. Herczeg;J. Bouwman;Joel D. Green;C. Dominik;T. Henning;S. Vicente;The Digit Team
作为DIGIT关键项目的一部分，我们展示了用Herschel/PACS拍摄的年轻主序前恒星的远红外（50−200 μm）光谱观测。样品包括16个Herbig AeBe和4个T Tauri源，在SED模式下观测到，覆盖整个光谱范围。在光谱覆盖范围有限的SED模式下还观测到了另外6个Herbig AeBe和4个T Tauri系统。在源位置探测到多条原子精细结构和分子谱线：[O i]，[C ii]，CO，OH，H2 O，CH +，最常见的是[O i ]6 3μm谱线，其次是OH.与CO相反，在Herbig AeBe两个组（燃烧和非燃烧源）中都检测到OH。与OH线拟合的等温LTE平板模型表明，柱密度为10 13 < NOH < 10 16 cm-2，发射半径为15 < r < 100 Au，激发温度为100 < Tex < 400 K。我们使用非LTE代码RADEX来验证LTE假设。需要高气体密度（n ≥ 10 10 cm −3）才能重现观测结果。OH辐射因此来自于中间恒星距离的盘中的温暖层。通过多条朝向T Tauri系统AS 205、DG Tau、S CrA和RNO 90以及三个Herbig AeBe系统HD 104237、HD 142527、HD 163296的谱线（通过谱线叠加）检测到温暖的H2O排放。总的来说，赫比格AeBe源有更高的OH/H2O丰度比整个磁盘比金牛座T磁盘，从近红外到远红外波长。探测到远红外CH +发射朝向HD 100546和HD 97048。平板模型表明中等激发（特克斯<$100 K）和紧凑（r <$60 Au）的情况下，HD 100546的排放。离源[O i]排放检测到对DG头，其起源可能是流出与此源。[C ii]发射在空间上扩展到检测到该线的所有源。这表明并非所有的[C ii]发射都与盘有关，并且年轻恒星周围的扩散材料有很大的贡献。原子精细结构谱线（[O i ]6 3μm，[O i] 145 μm，[C ii]）的通量比用PDR模型分析，需要高气体密度（n 10 5 cm −3）和高紫外通量（Go 10 3 −10 7），这与大多数源的氧谱线的圆盘起源一致。
We present far-infrared (50−200 μm) spectroscopic observations of young pre-main-sequence stars taken with Herschel/PACS as part of the DIGIT key project. The sample includes 16 Herbig AeBe and 4 T Tauri sources observed in SED mode covering the entire spectral range. An additional 6 Herbig AeBe and 4 T Tauri systems have been observed in SED mode with a limited spectral coverage. Multiple atomic fine structure and molecular lines are detected at the source position: [O i], [C ii], CO, OH, H2O, CH + .T he most common feature is the [O i ]6 3μm line detected in almost all of the sources, followed by OH. In contrast with CO, OH is detected toward both Herbig AeBe groups (flared and non-flared sources). An isothermal LTE slab model fit to the OH lines indicates column densities of 10 13 < NOH < 10 16 cm −2 , emitting radii 15 < r < 100 AU and excitation temperatures 100 < Tex < 400 K. We used the non-LTE code RADEX to verify the LTE assumption. High gas densities (n ≥ 10 10 cm −3 ) are needed to reproduce the observations. The OH emission thus comes from a warm layer in the disk at intermediate stellar distances. Warm H2O emission is detected through multiple lines toward the T Tauri systems AS 205, DG Tau, S CrA and RNO 90 and three Herbig AeBe systems HD 104237, HD 142527, HD 163296 (through line stacking). Overall, Herbig AeBe sources have higher OH/H2O abundance ratios across the disk than do T Tauri disks, from near- to far-infrared wavelengths. Far-infrared CH + emission is detected toward HD 100546 and HD 97048. The slab model suggests moderate excitation (Tex ∼ 100 K) and compact (r ∼ 60 AU) emission in the case of HD 100546. Off-source [O i] emission is detected toward DG Tau, whose origin is likely the outflow associated with this source. The [C ii] emission is spatially extended in all sources where the line is detected. This suggests that not all [C ii] emission is associated with the disk and that there is a substantial contribution from diffuse material around the young stars. The flux ratios of the atomic fine structure lines ([O i ]6 3μm, [O i] 145 μm, [C ii]) are analyzed with PDR models and require high gas density (n 10 5 cm −3 ) and high UV fluxes (Go ∼ 10 3 −10 7 ), consistent with a disk origin for the oxygen lines for most of the sources.