SiO outflow signatures toward massive young stellar objects with linearly distributed methanol masers
SiO outflow signatures toward massive young stellar objects with linearly distributed methanol masers
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DOI：
10.1051/0004-6361:200810907
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发表时间：
2008-10
影响因子：
6.5
通讯作者：
J. Buizer;R. Redman;S. Longmore;J. Caswell;P. A. F. SOFIA-USRA;G. Observatory;Nrcc;U. Wales;Atnf
中科院分区：
文献类型：
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作者：
J. Buizer;R. Redman;S. Longmore;J. Caswell;P. A. F. SOFIA-USRA;G. Observatory;Nrcc;U. Wales;Atnf
语境。甲醇脉塞经常呈线性分布，并且假设这些脉塞追踪年轻大质量恒星周围的星周吸积盘。然而，最近对氢气发射的观察表明，流出物似乎与微波激射分布角相似，而不是像微波激射盘场景中预期的那样垂直。目标。这里提出的观察背后的主要动机是利用独立流出示踪剂（即 SiO2）的存在和形态来确定这些区域是否确实存在流出，以及它们是否与脉泽盘假设一致或不一致。方法。对于 10 个有 H2 排放的源，我们获得了 JCMT 单皿 SiO (6-5) 观测值来寻找该流出指标。我们通过 ATCA 干涉图对六个源的 (2-1) 线中的 SiO 发射进行后续观察。结果。 JCMT 观测在 10 个源中的 9 个源中检测到了 SiO (6-5) 谱线。所有具有明亮 SiO2 线的光源都显示出表明流出的宽线翼。 JCMT 观测到的一部分源的甲醇脉泽速度明显偏离其母云速度，这支持了这些源中的脉泽可能与星周盘无关的观点。 SiO2 发射的 ATCA 图显示，六个源中的五个确实有 SiO2 流出（唯一未检测到的源与 JCMT 观测中未检测到的源相同）。流出物的空间方向与描绘圆盘方向的甲醇微波激射器不一致。总的来说，这里提出的观察结果似乎提供了进一步的证据，反对线性分布的甲醇微波激射器通常追踪大质量年轻恒星周围星周盘的方向的假设。
Context. Methanol masers are often found in linear distributions, and it has been hypothesized that these masers trace circumstellar accretion disks around young massive stars. However, recent observations in H2 emission have shown what appear to be outflows at similar angles to the maser distribution angles, not perpendicular as expected in the maser-disk scenario. Aims. The main motivation behind the observations presented here is to use presence and morphology of an independent outflow tracer, namely SiO, to determine if there are indeed outflows present in these regions and if they are consistent or inconsistent with the maser-disk hypothesis. Methods. For ten sources with H2 emission, we obtained JCMT single-dish SiO (6–5) observations to search for this outflow indicator. We followed up those observations with ATCA interferometric mapping of the SiO emission in the (2–1) line in six sources. Results. The JCMT observations yielded a detection in the SiO (6–5) line in nine of the ten sources. All of the sources with bright SiO lines display broad line wings indicative of outflow. A subset of the sources observed with the JCMT have methanol maser velocities significantly offset from their parent cloud velocities, supporting the idea that the masers in these sources are likely not to be associated with circumstellar disks. The ATCA maps of the SiO emission show five of the six sources do indeed have SiO outflows (the only non-detection being the same source that was a non-detection in the JCMT observations). The spatial orientations of the outflows are not consistent with the methanol masers delineating disk orientations. Overall, the observations presented here seem to provide further evidence against the hypothesis that linearly distributed methanol masers generally trace the orientations of circumstellar disks around massive young stars.