AN ALMA SEARCH FOR SUBSTRUCTURE, FRAGMENTATION, AND HIDDEN PROTOSTARS IN STARLESS CORES IN CHAMAELEON I
AN ALMA SEARCH FOR SUBSTRUCTURE, FRAGMENTATION, AND HIDDEN PROTOSTARS IN STARLESS CORES IN CHAMAELEON I
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DOI：
10.3847/0004-637x/823/2/160
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发表时间：
2016-04
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通讯作者：
M. Dunham;S. Offner;J. Pineda;T. Bourke;J. Tobin;H. Arce;Xuepeng Chen;J. Francesco;D. Johnstone;Katherine I. Lee;P. Myers;D. Price;S. Sadavoy;S. Schnee
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作者：
M. Dunham;S. Offner;J. Pineda;T. Bourke;J. Tobin;H. Arce;Xuepeng Chen;J. Francesco;D. Johnstone;Katherine I. Lee;P. Myers;D. Price;S. Sadavoy;S. Schnee
我们提出了阿塔卡马大毫米/亚毫米阵列（ALMA） 106 GHz（波段3）连续调查在变色龙1号分子云密集核心的完整种群。我们在19个不同的目标域中共检测到24个连续源。所有已知的变色龙I中的0级和I级原恒星都被检测到，而我们样本中的56个无星核都未被检测到。我们表明，Spitzer+Herschel对变色龙1号原恒星的普查是完整的，原恒星核心被错误分类为无恒星核心的比率计算为<1/56，或<2%。我们使用合成观测表明，当中心密度超过~ 108 cm−3时，我们的ALMA观测可以探测到湍流破碎情景下的无星核心坍塌，确切的密度取决于观测几何形状。另一方面，Bonnor-Ebert球在中心密度至少高达1010 cm−3时仍未被探测到。我们的无星核非探测被用来推断，要么变色龙I的恒星形成速率正在下降，大多数无星核没有坍缩，这与之前的研究结果相匹配，要么无星核的演化由比湍流破碎情景（如Bonnor-Ebert球体）预测的更少的亚结构模型更准确地描述。我们概述了区分这两种可能性所需的未来工作。
We present an Atacama Large Millimeter/submillimeter Array (ALMA) 106 GHz (Band 3) continuum survey of the complete population of dense cores in the Chamaeleon I molecular cloud. We detect a total of 24 continuum sources in 19 different target fields. All previously known Class 0 and Class I protostars in Chamaeleon I are detected, whereas all of the 56 starless cores in our sample are undetected. We show that the Spitzer+Herschel census of protostars in Chamaeleon I is complete, with the rate at which protostellar cores have been misclassified as starless cores calculated as <1/56, or <2%. We use synthetic observations to show that starless cores collapsing following the turbulent fragmentation scenario are detectable by our ALMA observations when their central densities exceed ∼108 cm−3, with the exact density dependent on the viewing geometry. Bonnor–Ebert spheres, on the other hand, remain undetected to central densities at least as high as 1010 cm−3. Our starless core non-detections are used to infer that either the star-formation rate is declining in Chamaeleon I and most of the starless cores are not collapsing, matching the findings of previous studies, or that the evolution of starless cores are more accurately described by models that develop less substructure than predicted by the turbulent fragmentation scenario, such as Bonnor–Ebert spheres. We outline future work necessary to distinguish between these two possibilities.