Modeling the millimeter emission from the Cepheus A young stellar cluster: Evidence for large scale collapse
Modeling the millimeter emission from the Cepheus A young stellar cluster: Evidence for large scale collapse
复制标题
模拟仙王座的毫米发射 年轻的星团：大规模塌缩的证据
DOI：
10.1051/0004-6361:20035640
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发表时间：
2004
影响因子：
6.5
通讯作者：
Jonathan P. Williams
中科院分区：
文献类型：
--
作者：
S. Bottinelli;Jonathan P. Williams
证据的大规模流动的低密度气体到仙王座A年轻星团。K波段近红外和多跃迁CS和N2 H +毫米线发射的观测结果与大多数嵌入式恒星周围冷尘埃的亚毫米图有关。近红外辐射与尘埃峰相抵消，表明在核心的历史中星星形成的位置发生了变化。CS发射集中向核心中心，但在两个主要核心的N2 H +峰从中心偏移，相反的化学观察到低质量的核心。在该区域的西部边缘发现了一个无星的核心，具有强的CS但弱的N2 H +发射。在团簇形成核心上的平均CS（2-1）光谱是不对称的自吸收的，这表明了坠落。我们分析了大尺度动力学应用一维辐射传输代码的一个模型的球形核心与恒定的温度和线宽，并从档案$850~\mu$m地图的区域测量的密度分布。匹配三个CS配置文件的最佳拟合模型需要低CS丰度的核心和外部，下降信封具有低密度和未耗尽的CS丰度。两条N2 H +谱线的积分强度与恒定的N2 H +丰度很好地匹配。包线下落速度受到CS（2-1）不对称性的严格约束，并且是亚音速的，但是下落区域的大小很难确定。一个高密度中心耗尽CS缓慢吸积一个低密度外壳正常CS丰度的图片表明，核心增长发生至少部分的大尺度上的湍流支持的耗散。
Evidence for a large scale flow of low density gas onto the Cepheus A young stellar cluster is presented. Observations of K -band near-infrared and multi-transition CS and N 2 H + millimeter line emission are shown in relation to a sub-millimeter map of the cool dust around the most embedded stars. The near-infrared emission is offset from the dust peak suggesting a shift in the location of star formation over the history of the core. The CS emission is concentrated toward the core center but N 2 H + peaks in two main cores offset from the center, opposite to the chemistry observed in low mass cores. A starless core with strong CS but weak N 2 H + emission is found toward the western edge of the region. The average CS(2–1) spectrum over the cluster forming core is asymmetrically self-absorbed suggesting infall. We analyze the large scale dynamics by applying a one-dimensional radiative transfer code to a model spherical core with constant temperature and linewidth, and a density profile measured from an archival $850~\mu$m map of the region. The best fit model that matches the three CS profiles requires a low CS abundance in the core and an outer, infalling envelope with a low density and undepleted CS abundance. The integrated intensities of the two N 2 H + lines is well matched with a constant N 2 H + abundance. The envelope infall velocity is tightly constrained by the CS(2–1) asymmetry and is sub-sonic but the size of the infalling region is poorly determined. The picture of a high density center with depleted CS slowly accreting a low density outer envelope with normal CS abundance suggests that core growth occurs at least partially by the dissipation of turbulent support on large scales.