SUBSTELLAR-MASS CONDENSATIONS IN PRESTELLAR CORES
SUBSTELLAR-MASS CONDENSATIONS IN PRESTELLAR CORES
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DOI：
10.1088/2041-8205/758/2/l25
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发表时间：
2012-09
期刊：
影响因子：
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通讯作者：
F. Nakamura;S. Takakuwa;R. Kawabe
中科院分区：
文献类型：
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作者：
F. Nakamura;S. Takakuwa;R. Kawabe
我们展示了向最近的星团形成区域 ρ Ophiuchus 中的两个前恒星核心 SM1 和 B2-N5 发射的（亚）毫米尘埃连续谱的亚毫米阵列和单碟图像组合。我们的组合图像表明，SM1 和 B2-N5 分别由三个和四个凝结组成，质量为 10−2–10−1 M☉，大小为几百个天文单位。单个凝聚的平均密度为108-109 cm−3，质量相当于或大于临界邦纳-埃伯特质量，表明自重力在凝聚的动力学演化中起着重要作用。这些凝聚的合并时间尺度估计约为 104 年，与局部引力塌缩时间尺度相当，这表明凝聚的合并而不是吸积在恒星形成过程中发挥着重要作用。这些结果挑战了恒星形成的标准理论，在该理论中，一个相当无特征的前恒星核心坍缩最多形成几次凝聚，每一个凝聚都有可能演化成一颗原恒星，原恒星被旋转的圆盘包围，行星就是在旋转的圆盘周围形成的。
We present combined Submillimeter Array and single-dish images of the (sub)millimeter dust continuum emission toward two prestellar cores, SM1 and B2-N5, in the nearest star-cluster-forming region, ρ Ophiuchus. Our combined images indicate that SM1 and B2-N5 consist of three and four condensations, respectively, with masses of 10−2–10−1 M☉ and sizes of a few hundred AU. The individual condensations have mean densities of 108–109 cm−3 and the masses are comparable to or larger than the critical Bonner–Ebert mass, indicating that self-gravity plays an important role in the dynamical evolution of the condensations. The coalescence timescale of these condensations is estimated to be about 104 yr, which is comparable to the local gravitational collapse timescale, suggesting that merging of the condensations, instead of accretion, plays an essential role in the star formation process. These results challenge the standard theory of star formation, where a single, rather featureless, prestellar core collapses to form at most a couple of condensations, each of which potentially evolves into a protostar that is surrounded by a rotating disk where planets are created.