The RMS survey : 13CO observations of candidate massive YSOs in the northern Galactic plane
The RMS survey : 13CO observations of candidate massive YSOs in the northern Galactic plane
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DOI：
10.1051/0004-6361:200809415
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发表时间：
2007-11
影响因子：
6.5
通讯作者：
J. Urquhart;A. L. Busfield;M. Hoare;S. Lumsden;R. Oudmaijer;T. Moore;A. Gibb;C. Purcell;M. Burton;L. Mar'echal;Z. Jiang;M. Leeds;Liverpool John Moores University;U. Columbia;U. Wales;Jodrell Bank Observatory;'Ecole Normale Sup'erieure;Purple Mountain Observatory
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作者：
J. Urquhart;A. L. Busfield;M. Hoare;S. Lumsden;R. Oudmaijer;T. Moore;A. Gibb;C. Purcell;M. Burton;L. Mar'echal;Z. Jiang;M. Leeds;Liverpool John Moores University;U. Columbia;U. Wales;Jodrell Bank Observatory;'Ecole Normale Sup'erieure;Purple Mountain Observatory
语境。红色 MSX 源 (RMS) 巡天是一项正在进行的多波长观测计划，旨在返回大量精心挑选的大质量年轻恒星物体 (MYSO) 样本。通过将 MSX 和 2MASS 点源的颜色与已知 MYSO 的颜色进行比较，我们已经确定了位于银河系内的 ∼2000 个 MYSO 候选者。我们后续观测的目的是识别其他污染天体，例如超致密 (UC) HII 区域、演化恒星和行星状星云 (PNe)，并区分真正的 MYSO 和附近的低质量 YSO。目标。我们后续计划的一个关键部分是进行 13 个 CO 分子线观测，以确定与所有 MYSO 候选者的运动距离。这些距离将与远红外和（亚）毫米通量结合使用，以确定辐射光度，这将使我们能够识别和消除附近的低质量 YSO。此外，这些分子线观测将有助于识别弱二氧化碳排放者的演化恒星。方法。我们利用22 m Mopra望远镜、15 m JCMT和20 m Onsala望远镜对位于第三和第四象限的854个MYSO候选体进行了分子线观测。这些观测是在 13 个 CO 分子的 J = 1–0（Mopra 和 Onsala）和 J = 2–1 (JCMT) 旋转跃迁频率下进行的，空间分辨率为 ∼20 �� −40 �� ，灵敏度为 T ∗ A � 0.1 K ，速度分辨率为 ∼0.2 km s −1 。结果。我们在观察到的 854 个 RMS 源中总共 752 个中检测到了 13 个 CO 排放（~88%）。总共检测到 2132 个发射成分高于 3σ 水平（通常 T ＊ ≥ 0.3 K）。对其中大多数源（461 个源（∼60%））观察到多种发射剖面，沿视线平均检测到 ∼4 个分子云。这些多重发射特征使得我们很难为我们的许多样本分配运动速度。我们使用档案 CS (J = 2–1) 和脉泽速度来解析 82 个源的分量多重性，并得出一个标准，用于识别另外 218 个多分量源的最可能分量。结合单分量检测，我们获得了 591 个源的明确运动速度（约 80% 的检测）。我们无法确定运动速度的 161 个源将需要额外的线数据。使用 Brand & Blitz (1993) 的旋转曲线及其径向速度，我们计算了所有检测到的组件的运动距离。
Context. The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). We have identified ∼2000 MYSOs candidates located within our Galaxy by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. The aim of our follow-up observations is to identify other contaminating objects such as ultra compact (UC) HII regions, evolved stars and planetary nebulae (PNe) and distinguish between genuine MYSOs and nearby low-mass YSOs. Aims. A critical part of our follow-up programme is to conduct 13 CO molecular line observations in order to determine kinematic distances to all of our MYSO candidates. These distances will be used in combination with far-IR and (sub)millimetre fluxes to determine bolometric luminosities which will allow us to identify and remove nearby low-mass YSOs. In addition these molecular line observations will help in identifying evolved stars which are weak CO emitters. Methods. We have used the 22 m Mopra telescope, the 15 m JCMT and the 20 m Onsala telescope to conduct molecular line observations towards 854 MYSOs candidates located in the 3rd and 4th quadrants. These observations have been made at the J = 1–0 (Mopra and Onsala) and J = 2–1 (JCMT) rotational transition frequency of 13 CO molecules and have a spatial resolution of ∼20 �� −40 �� ,a sensitivity of T ∗ A � 0.1 K and a velocity resolution of ∼0.2 km s −1 . Results. We detect 13 CO emission towards a total of 752 of the 854 RMS sources observed (∼88%). In total 2132 emission components are detected above 3σ level (typically T ∗ ≥ 0.3 K). Multiple emission profiles are observed towards the majority of these sources – 461 sources (∼60%) – with an average of ∼4 molecular clouds detected along the line of sight. These multiple emission features make it difficult to assign a kinematic velocity to many of our sample. We have used archival CS (J = 2–1) and maser velocities to resolve the component multiplicity towards 82 sources and have derived a criterion which is used to identify the most likely component for a further 218 multiple component sources. Combined with the single component detections we have obtained unambiguous kinematic velocities towards 591 sources (∼80% of the detections). The 161 sources for which we have not been able to determine the kinematic velocity will require additional line data. Using the rotation curve of Brand & Blitz (1993) and their radial velocities we calculate kinematic distances for all components detected.