SOLIS: XVI. Mass ejection and time variability in protostellar outflows: Cep E
SOLIS: XVI. Mass ejection and time variability in protostellar outflows: Cep E
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索利斯：十六。
DOI：
10.1051/0004-6361/202142931
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发表时间：
2022
影响因子：
6.5
通讯作者：
De Simone, M.
中科院分区：
文献类型：
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作者：
de A. Schutzer, A.;Rivera-Ortiz, P. R.;Lefloch, B.;Gusdorf, A.;Favre, C.;Segura-Cox, D.;López-Sepulcre, A.;Neri, R.;Ospina-Zamudio, J.;De Simone, M.
原恒星喷流是恒星形成反馈的重要媒介，与质量吸积过程密切相关。射流形成和物质抛射的历史为质量吸积历史和驱动源的性质提供了约束。目的描述0级原恒星阶段物质抛射现象的时变特征，以便更好地了解流出气体的动力学，并对喷射化学成分的起源和质量吸积历史提供更多的约束。方法利用北方扩展毫米波阵列（NOEMA）干涉仪，分别以1.0″（820 au）和0.4″（330 au）的角分辨率观测了CO 2-1和SONJ= 54 - 43旋转跃迁向中质量0级原恒星系统Cep e .结果CO高速射流发射揭示了一个直径≤400 au的中心分量，与高速分子结有关，在SO中也检测到。被一层夹带气体包围。气体层沿主轴加速，长度范围为δ0~ 700 au，而其直径在距原恒星2000 au时逐渐增加到1000 au。喷流被分割成18节的质量~10−3M⊙，不均匀地分布在南北叶之间，速度变化高达15 km s−1，接近原恒星。这远低于北部叶（+ 65 km s - 1）和南部叶（- 125 km s - 1）的射流终端速度。在~50 ~ 80 yr的时间尺度上，结段分布近似为双峰分布，接近于喷射驱动的原恒星Cep E-A和~150 ~ 20 yr的更大距离>12″。结质量的损失率总体上是稳定的，北叶和南叶的损失率分别为2.7 × 10−5M⊙yr−1和8.9 × 10−6M⊙yr−1。结论周围原恒星物质与高速结的相互作用驱动了射流周围分子层的形成。这就解释了北半球较高的质量损失率。用一个周期为2000年和物质抛射周期为55年的简单岁差模型可以很好地解释喷流动力学。
ContextProtostellar jets are an important agent of star formation feedback, tightly connected with the mass-accretion process. The history of jet formation and mass ejection provides constraints on the mass accretion history and on the nature of the driving source.AimsWe characterize the time-variability of the mass-ejection phenomena at work in the class 0 protostellar phase in order to better understand the dynamics of the outflowing gas and bring more constraints on the origin of the jet chemical composition and the mass-accretion history.MethodsUsing the NOrthern Extended Millimeter Array (NOEMA) interferometer, we have observed the emission of the CO 2–1 and SONJ= 54–43rotational transitions at an angular resolution of 1.0″ (820 au) and 0.4″ (330 au), respectively, toward the intermediate-mass class 0 protostellar system Cep E.ResultsThe CO high-velocity jet emission reveals a central component of ≤400 au diameter associated with high-velocity molecular knots that is also detected in SO, surrounded by a collimated layer of entrained gas. The gas layer appears to be accelerated along the main axis over a length scaleδ0~ 700 au, while its diameter gradually increases up to several 1000 au at 2000 au from the protostar. The jet is fragmented into 18 knots of mass ~10−3M⊙, unevenly distributed between the northern and southern lobes, with velocity variations up to 15 km s−1close to the protostar. This is well below the jet terminal velocities in the northern (+ 65 km s−1) and southern (−125 km s−1) lobes. The knot interval distribution is approximately bimodal on a timescale of ~50–80 yr, which is close to the jet-driving protostar Cep E-A and ~150–20 yr at larger distances >12″. The mass-loss rates derived from knot masses are steady overall, with values of 2.7 × 10−5M⊙yr−1and 8.9 × 10−6M⊙yr−1in the northern and southern lobe, respectively.ConclusionsThe interaction of the ambient protostellar material with high-velocity knots drives the formation of a molecular layer around the jet. This accounts for the higher mass-loss rate in the northern lobe. The jet dynamics are well accounted for by a simple precession model with a period of 2000 yr and a mass-ejection period of 55 yr.