Effects of non-uniform interstellar magnetic field on synchrotron X-ray and inverse-Compton γ-ray morphology of supernova remnants
Effects of non-uniform interstellar magnetic field on synchrotron X-ray and inverse-Compton γ-ray morphology of supernova remnants
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DOI：
10.1051/0004-6361/201015505
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发表时间：
2010-11
影响因子：
6.5
通讯作者：
S. Orlando;O. Petruk;F. Bocchino;M. Miceli
中科院分区：
文献类型：
--
作者：
S. Orlando;O. Petruk;F. Bocchino;M. Miceli
上下文X射线和γ射线波段超新星遗迹（SNRs）的观测有望为我们理解强非相对论冲击附近带电粒子和磁场的运动学以及银河宇宙线的性质提供重要信息。为了准确分析不同能带的信噪比图像，需要对信噪比的同步辐射和逆康普顿辐射进行理论建模。目标。我们开发了一个数值代码（remlight），从MHD模拟，合成的同步辐射，X射线，和逆康普顿γ射线发射起源于SNR扩展在非均匀星际介质（ISM）和/或非均匀星际磁场（ISMF）。作为第一个应用程序，该代码被用来研究非均匀ISMF的SNR形态在非热X射线和γ射线波段的影响。方法.我们进行三维MHD模拟球形SNR冲击扩展通过磁化ISM与环境磁场强度的梯度。该模型包括一个近似的处理上游磁场放大和冲击修改由于加速宇宙射线的反反应的效果，假设这两种效果是各向同性的。从模拟中，我们合成同步辐射，X射线和逆康普顿γ射线发射与合成代码remlight，对加速和相对论电子注入的细节做不同的假设。结果如果环境磁场强度的梯度具有垂直于视线（LoS）的分量，则环境磁场强度的梯度在无线电、硬X射线和γ射线波段中诱导不对称形态，而与电子注入模型无关。残余物形态的不对称程度取决于电子注入和加速的细节，并且在射电、硬X射线和γ射线波段中是不同的。一般来说，非热X射线形态对梯度最敏感，表现出最高程度的不对称性。IC γ射线发射对非均匀ISMF的敏感性较弱，残余形貌的不对称程度在该波段最低。
Context. Observations of SuperNova Remnants (SNRs) in X-ray and γ-ray bands promise to contribute important information to our understanding of the kinematics of charged particles and magnetic fields in the vicinity of strong non-relativistic shocks and, therefore, the nature of Galactic cosmic rays. The accurate analysis of SNR images collected in different energy bands requires theoretical modeling of synchrotron and inverse Compton emission from SNRs. Aims. We develop a numerical code (remlight) to synthesize, from MHD simulations, the synchrotron radio, X-ray, and inverse Compton γ-ray emission originating in SNRs expanding in a non-uniform interstellar medium (ISM) and/or non-uniform interstellar magnetic field (ISMF). As a first application, the code is used to investigate the effects of non-uniform ISMF on the SNR morphology in the non-thermal X-ray and γ-ray bands. Methods. We perform 3D MHD simulations of a spherical SNR shock expanding through a magnetized ISM with a gradient of ambient magnetic field strength. The model includes an approximate treatment of upstream magnetic field amplification and the effect of shock modification due to the back reaction of accelerated cosmic rays, assuming both effects to be isotropic. From the simulations, we synthesize the synchrotron radio, X-ray, and inverse Compton γ-ray emission with the synthesis code remlight ,m aking different assumptions about the details of acceleration and the injection of relativistic electrons. Results. A gradient in the ambient magnetic field strength induces asymmetric morphologies in radio, hard X-ray, and γ-ray bands independently of the model of electron injection if the gradient has a component perpendicular to the line-of-sight (LoS). The degree of asymmetry of the remnant morphology depends on the details of the electron injection and acceleration and is different in the radio, hard X-ray, and γ-ray bands. In general, the non-thermal X-ray morphology is the most sensitive to the gradient, showing the highest degree of asymmetry. The IC γ-ray emission is weakly sensitive to the non-uniform ISMF, the degree of asymmetry of the remnant morphology being the lowest in this band.