标题： 探测星团形成中的中间到高质量恒星：NGC 2264星团块的详细毫米波研究 显示英文标题

标题： Probing the formation of intermediate- to high-mass stars in protoclusters: A detailed millimeter study of the NGC 2264 clumps

摘要： 我们展示了对两个大质量星团形成云核 NGC 2264-C 和 NGC 2264-D 的尘埃连续谱和分子线观测结果，包括使用 IRAM 30 米望远镜上的 MAMBO 热电偶阵列和 HERA 频谱阵列进行的大范围测绘。这两个 NGC 2264 云核位于邻近的 Mon OB1 巨分子云复合体中。分别在云核 C 和 D 中识别出 12 个和 15 个致密毫米波连续谱源（即 MMS）。在 NGC 2264-C 和 NGC 2264-D 中发现了广泛的吸积运动迹象，例如在 HCO+(3-2) 或 CS(3-2) 中。在 NGC 2264-C 的中心最内层区域，观测到 N_2H+(1-0) 和 H^{13}CO+(1-0) 中约 2 公里每秒幅度的明显速度间断，我们认为这是两个 MMS 与其可能合并至中心 MMS C-MM3 的强烈动力学相互作用的标志。辐射转移建模支持 NGC 2264-C 是一个高度不稳定的长轴坍塌的椭球形云核，在接近自由落体的动力学时间尺度（约 1.7×10^5 年）上进行坍缩。我们的大规模坍缩模型拟合表明，向中心原恒星天体 C-MM3 的最大物质流入率约为 3×10^{-3}太阳质量每年。这种吸积率足够高，能够克服辐射压力，并在约 1.7×10^5 年的时间内通过吸积形成约 20 太阳质量的恒星。这与 NGC 2264-C 中心部分的整体动力学时间尺度相似。我们得出结论，我们很可能正在见证 NGC 2264-C 中央部分高质量（> 10 太阳质量）原恒星的形成。我们的结果表明了介于 Bonnell 等人（1998）提出的恒星合并场景和 McKee & Tan（2003）提出的巨大湍流核心模型之间的大质量恒星形成图景。 显示英文摘要

摘要： We present the results of dust continuum and molecular line observations of two massive cluster-forming clumps, NGC 2264-C and NGC 2264-D, including extensive mapping performed with the MAMBO bolometer array and the HERA heterodyne array on the IRAM 30m telescope. Both NGC 2264 clumps are located in the Mon OB1 giant molecular cloud complex, adjacent to one another. Twelve and fifteen compact millimeter continuum sources (i.e. MMSs) are identified in clumps C and D, respectively. Evidence for widespread infall motions is found in, e.g., HCO+(3-2) or CS(3-2) in both NGC 2264-C and NGC 2264-D. A sharp velocity discontinuity ~ 2 km/s in amplitude is observed in N_2H+(1-0) and H^{13}CO+(1-0) in the central, innermost part of NGC 2264-C, which we interpret as the signature of a strong dynamical interaction between two MMSs and their possible merging with the central MMS C-MM3. Radiative transfer modelling supports the idea that NGC 2264-C is a highly unstable prolate clump in the process of collapsing along its long axis on a near free-fall dynamical timescale ~ 1.7x10^5 yr. Our model fit of this large-scale collapse suggests a maximum mass inflow rate ~ 3x10^{-3} Msun/yr toward the central protostellar object C-MM3. Such infall rates are sufficiently high to overcome radiation pressure and allow the formation of ~ 20 Msun stars by accretion in ~ 1.7x10^5 yr, i.e., a time similar to the global dynamical timescale of the central part of NGC 2264-C. We conclude that we are likely witnessing the formation of a high-mass (> 10 Msun) protostar in the central part of NGC 2264-C. Our results suggest a picture of massive star formation intermediate between the scenario of stellar mergers of Bonnell et al. (1998) and the massive turbulent core model of McKee & Tan (2003).