ICM-SHOX III. MACS J0018.5+1626 案例研究：一个看起来像无线电晕的无线电余辉？
ICM-SHOX III. The case of MACS J0018.5+1626, a radio relic that looks like a radio halo?
AI总结：
ICM-SHOX项目通过三维磁流体动力学模拟揭示MACS J0018.5+1626的双星系合并过程，发现其无线电余辉可能由两个近似正面观测的余辉叠加形成。
摘要：
我们首次对MACS J0018.5+1626的无线电发射进行了详细的数值建模，作为改进合并约束（ICM-SHOX）项目的一部分。通过将X射线、热和动能Sunyaev-Zel'dovich、光学和透镜观测数据与模拟匹配，ICM-SHOX流程表明MACS J0018.5+1626正处于双星系合并接近近日点，并且沿着几乎与合并轴对齐的视线观测。我们进行了三维磁流体动力学模拟，结合追踪粒子和福克-普朗克求解器，以建模无线电发射。探索ICM-SHOX参数空间中最可能的初始条件变化，如星系团相对速度和冲击参数，我们发现所得到的合并配置一致产生两个由合并驱动的冲击波，其典型平均马赫数$\mathcal{M}_s \sim 2$--$3$，对应的标准差为$σ_{\mathcal{M}} \sim 0.5$--$1.5$。在此框架内，我们研究了在何种星系团条件下，标准扩散冲击加速可以重现LOFAR观测。特别是，我们讨论了LOFAR观测到的看似无线电晕可能是两个近似正面观测的无线电余辉叠加的可能性。
英文摘要：
We present the first detailed numerical modeling of the radio emission from MACS J0018.5+1626 as part of the Improved Constraints on Mergers with SZ, Hydrodynamical simulations, Optical, and X-ray (ICM-SHOX) project. By matching X-ray, thermal and kinetic Sunyaev--Zel'dovich, optical and lensing observables to simulations, the ICM-SHOX pipeline indicates that MACS J0018.5+1626 is undergoing a binary merger close to pericenter passage and is observed along a line of sight nearly aligned with the merger axis. We perform three-dimensional magnetohydrodynamic simulations of binary cluster mergers coupled to tracer particles and a Fokker--Planck solver to model the radio emission. Exploring variations in the most likely initial conditions within the ICM-SHOX parameter space, such as the relative cluster velocity and impact parameter, we find that the resulting merger configuration consistently produces two merger-driven shocks with typical average Mach numbers $\mathcal{M}_s \sim 2$--$3$ with corresponding standard deviations of $σ_{\mathcal{M}} \sim 0.5$--$1.5$. Within this framework, we examine the cluster conditions under which standard diffusive shock acceleration can reproduce LOFAR observations. In particular, we discuss the possibility that the apparent radio halo seen by LOFAR arises from the superposition of two radio relics viewed nearly face-on.
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