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arXiv 2009.06649astro-ph.HE
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壳型超新星遗迹的TeV gamma-ray形貌模拟

Simulating TeV gamma-ray morphologies of shell-type supernova remnants

Matteo Pais, Christoph Pfrommer

摘要:

超新星遗迹(SNR)冲击提供了有利的网站宇宙线(CR)质子加速,如果当地的磁场方向是准平行的冲击法向。使用移动网格磁流体动力学(MHD)代码AREPO,我们提出了一套SNR模拟与CR加速在Sedov-Taylor阶段,结合不同的磁场拓扑结构,密度分布与梯度和大规模的波动,和-为我们的核心崩溃SNR-一个多相星际介质与致密团块的对比度$10^4$。假设强子γ射线发射模型的TeV γ射线发射,我们发现,大幅度的密度波动的$δρ/ρ_0\gtrsim75$百分之强烈调制的γ射线发射率在稻草人的模型中,其中的加速效率是独立的磁性。然而,这会导致激波表面产生强烈的波纹,而这些波纹被伽马射线观测所排除。相比之下,磁致伸缩性依赖的加速可以很容易地解释从SN 1006(具有均匀磁场)到Vela Junior和RX J1713(具有湍流场)的伽马射线形态中观察到的变化,该模型来自等离子体粒子模拟。我们对SN 1006的最佳拟合模型具有从西南指向东北的大尺度密度梯度$ \nabla{n}\simeq 0.0034~\mathrm{cm}^{-3}~\mathrm{pc}^{-1} $和与天空平面的磁倾角$\lesssim10^\circ$。Vela Junior和RX J1713的最佳拟合模型采用湍流磁场和致密团块的组合来解释它们的TeV伽马射线形态和中等激波波纹。

英文摘要:

Supernova remnant (SNR) shocks provide favourable sites of cosmic ray (CR) proton acceleration if the local magnetic field direction is quasi-parallel to the shock normal. Using the moving-mesh magneto-hydrodynamical (MHD) code AREPO we present a suite of SNR simulations with CR acceleration in the Sedov-Taylor phase that combine different magnetic field topologies, density distributions with gradients and large-scale fluctuations, and -- for our core-collapse SNRs -- a multi-phase interstellar medium with dense clumps with a contrast of $10^4$. Assuming the hadronic gamma-ray emission model for the TeV gamma-ray emission, we find that large-amplitude density fluctuations of $δρ/ρ_0\gtrsim75$ per cent are required to strongly modulate the gamma-ray emissivity in a straw man's model in which the acceleration efficiency is independent of magnetic obliquity. However, this causes strong corrugations of the shock surface that are ruled out by gamma-ray observations. By contrast, magnetic obliquity-dependent acceleration can easily explain the observed variance in gamma-ray morphologies ranging from SN1006 (with a homogeneous magnetic field) to Vela Junior and RX J1713 (with a turbulent field) in a single model that derives from plasma particle-in-cell simulations. Our best-fit model for SN1006 has a large-scale density gradient of $ \nabla{n}\simeq 0.0034~\mathrm{cm}^{-3}~\mathrm{pc}^{-1} $ pointing from south-west to north-east and a magnetic inclination with the plane of the sky of $\lesssim10^\circ$. Our best-fit model for Vela Junior and RX J1713 adopts a combination of turbulent magnetic field and dense clumps to explain their TeV gamma-ray morphologies and moderate shock corrugations.

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