The Shape of Cas A
The Shape of Cas A
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Cas A的形状
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
S. Couch
中科院分区：
文献类型：
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作者：
C. Wheeler;J. Maund;S. Couch
在光学，红外和X射线研究的基础上，Cas A，我们提出了一个几何形状的残余物的基础上的“喷气诱导”的情况下，显着的系统偏离轴对称。在这个模式中，主急流轴在北偏东110° ~ 120 °，视线偏东40° ~ 50 °处，朝向强蓝移运动方向。正如喷气诱导模型所预测的那样，垂直于该轴的是一个膨胀的圆环体。在所提出的几何形状中，主喷流中的铁峰元素可能会出现“超越”富含硅的残留物部分的投影效应，而不是混合效应。在所提出的几何学的背景下，如果紧凑型物体的运动接近但稍微偏离主“喷流”轴的方向约30°，则可以容纳紧凑型物体从残余物的运动中心以~169°的位置角的位移。在这个模型中，经典的东北“喷流”、西南“反喷流”和其他突出物，特别是北部的“洞”，是近似在赤道平面内的非轴对称流动，例如，从膨胀的环面的周边向外，而不是与主射流相关联。我们探讨了轮辐流在赤道平面的瑞利-泰勒，Richtmyer-Meshkov，和开尔文-亥姆霍兹不稳定性，并说明这些不稳定性与射流诱导的模拟。
On the basis of optical, IR, and X-ray studies of Cas A, we propose a geometry for the remnant based on a “jet-induced” scenario with significant systematic departures from axial symmetry. In this model, the main jet axis is oriented in the direction of strong blueshifted motion at an angle of 110°-120° east of north and about 40°-50° to the east of the line of sight. Normal to this axis would be an expanding torus as predicted by jet-induced models. In the proposed geometry, iron-peak elements in the main jetlike flow could appear “beyond” the portions of the remnant rich in silicon by projection effects, not the effect of mixing. In the context of the proposed geometry, the displacement of the compact object from the kinematic center of the remnant at a position angle of ~169° can be accommodated if the motion of the compact object is near to, but slightly off from, the direction of the main “jet” axis by of order 30°. In this model, the classical NE “jet,” the SW “counterjet,” and other protrusions, particularly the “hole” in the north, are nonaxisymmetric flows approximately in the equatorial plane, e.g., out through the perimeter of the expanding torus, rather than being associated with the main jet. We explore the spokelike flow in the equatorial plane in terms of Rayleigh-Taylor, Richtmyer-Meshkov, and Kelvin-Helmholz instabilities and illustrate these instabilities with a jet-induced simulation.