High Angular Resolution Observations Towards OMC-2 FIR 4: Dissecting an Intermediate-Mass Protocluster
High Angular Resolution Observations Towards OMC-2 FIR 4: Dissecting an Intermediate-Mass Protocluster
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DOI：
10.1051/0004-6361/201220905
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发表时间：
2013-04
影响因子：
6.5
通讯作者：
A. López-Sepulcre;V. Taquet;Á. Sánchez-Monge;C. Ceccarelli;C. Dominik;C. Dominik;M. Kama;E. Caux;E. Caux;F. Fontani;A. Fuente;Paul T. P. Ho;Paul T. P. Ho;R. Neri;Y. Shimajiri
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文献类型：
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作者：
A. López-Sepulcre;V. Taquet;Á. Sánchez-Monge;C. Ceccarelli;C. Dominik;C. Dominik;M. Kama;E. Caux;E. Caux;F. Fontani;A. Fuente;Paul T. P. Ho;Paul T. P. Ho;R. Neri;Y. Shimajiri
上下文中等质量恒星是银河系的重要组成部分，也是理解高质量和低质量恒星如何形成星团的关键。已知最接近的年轻中等质量原星团之一是OMC-2 FIR 4，它位于猎户座中420 pc的距离。这一区域是用赫歇尔卫星上的外差光谱仪HIFI观测到500-2000 GHz完整光谱的少数区域之一，并用JCMT和IRAM 30米望远镜获得了0.8、1、2和3毫米的无偏光谱测量。目标。我们的目标是解开核心的多样性，调查这一地区的形态，以研究形成一个低质量和中等质量的原星团，并帮助解释已经在我们手中的单碟线配置文件。方法.我们使用IRAM Plateau de Bure干涉仪对OMC-2 FIR 4在2 mm连续发射以及DCO +（2-1）、DCN（2-1）、C 34 S（3-2）和几条CH 3OH谱线中的图像进行了成像。此外，我们分析了NH3（1，1）和（2，2）反转跃迁的观测结果，使用NRAO的超大阵列。由此产生的地图有一个角分辨率，使我们能够解决结构的5 θ，这相当于10000 Au。结果我们的观测揭示了OMC-2 FIR 4内的三个空间分辨源，每个源有一个或几个太阳质量，并暗示了其中进一步未解决的子结构。其中两个源具有细长的形状，并与尘埃连续发射峰相关，因此每个源可能包含至少一个分子核心。其中一颗还显示出射电连续辐射，这可能是由一颗年轻的B3-B4星星造成的，它主导了该区域的整体光度输出。第三个已识别的源显示DCO +（2-1）发射峰和弱尘埃连续发射。相对于其他两个区域，它更高的DCO +丰度表明温度较低，因此它可能与一个更年轻的低质量原恒星或无星核心有关。它也可以是OMC-2 FIR 4的较冷包封的一部分。结论.我们的干涉观测显示了中等质量原星团OMC-2 FIR 4的复杂性，其中多个核心，化学分化，和电离区都共存的面积只有10 000 Au。
Context. Intermediate-mass stars are an important ingredient of our Galaxy and a key to understanding how high- and low-mass stars form in clusters. One of the closest known young intermediate-mass protoclusters is OMC-2 FIR 4, which is located at a distance of 420 pc in Orion. This region is one of the few where the complete 500–2000 GHz spectrum has been observed with the heterodyne spectrometer HIFI on board the Herschel satellite, and unbiased spectral surveys at 0.8, 1, 2, and 3 mm have been obtained with the JCMT and IRAM 30-m telescopes. Aims. We aim to disentangle the core multiplicity, to investigate the morphology of this region in order to study the formation of a low- and intermediate-mass protostar cluster, and to aid in interpretation of the single-dish line profiles already in our hands. Methods. We used the IRAM Plateau de Bure Interferometer to image OMC-2 FIR 4 in the 2-mm continuum emission, as well as in DCO + (2–1), DCN(2–1), C 34 S(3–2), and several CH3OH lines. In addition, we analysed observations of the NH3(1, 1) and (2, 2) inversion transitions that used the Very Large Array of the NRAO. The resulting maps have an angular resolution that allows us to resolve structures of 5 �� , which is equivalent to ∼2000 AU. Results. Our observations reveal three spatially resolved sources within OMC-2 FIR 4, of one or several solar masses each, with hints of further unresolved substructure within them. Two of these sources have elongated shapes and are associated with dust continuum emission peaks, thus likely containing at least one molecular core each. One of them also displays radio continuum emission, which may be attributed to a young B3–B4 star that dominates the overall luminosity output of the region. The third identified source displays a DCO + (2–1) emission peak and weak dust continuum emission. Its higher abundance of DCO + relative to the other two regions suggests a lower temperature, hence its possible association with either a younger low-mass protostar or a starless core. It may alternatively be part of the colder envelope of OMC-2 FIR 4. Conclusions. Our interferometric observations show the complexity of the intermediate-mass protocluster OMC-2 FIR 4, where multiple cores, chemical differentiation, and an ionised region all coexist within an area of only 10 000 AU.