First predicted cosmic ray spectra, primary-to-secondary ratios, and ionization rates from MHD galaxy formation simulations
First predicted cosmic ray spectra, primary-to-secondary ratios, and ionization rates from MHD galaxy formation simulations
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首次通过 MHD 星系形成模拟预测宇宙射线光谱、初级与次级比率和电离率
DOI：
10.1093/mnras/stac1791
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发表时间：
2022
影响因子：
4.8
通讯作者：
Kereš, Dušan
中科院分区：
文献类型：
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作者：
Hopkins, Philip F.;Butsky, Iryna S.;Panopoulou, Georgia V.;Ji, Suoqing;Quataert, Eliot;Faucher-Giguère, Claude-André;Kereš, Dušan
我们提出了第一个模拟进化解决的宇宙射线（CR）从MeV-TeV的能量（包括电子，正电子，（反）质子，和较重的原子核），在现场的动力学磁流体力学星系模拟与星星的形成和反馈的光谱。我们利用新的数值方法，包括在历史模型中经常被忽视的条款，比较银河系类似物与现象学散射系数ν太阳附近[本地星际介质（LISM）]的观测（光谱，B/C，e+/e−，10 Be/9 Be，电离和γ射线）。我们表明，它是可能的重现观察与简单的单幂律注入和散射系数（缩放与rigidityR），类似于以前的（非动力学）计算。我们还发现：（1）实际星系中的环星系介质必然会产生ankpc CR散射晕，从而影响所需的ν（R）。(2)增加ν（R）的归一化使CR次级谱重新归一化，但由于源分布和损失效应，也改变了初级谱斜率。(3)扩散/湍流再加速是不重要的，一般是次主导的回转共振/流动损失，这是次主导的绝热/对流项占主导地位的kpc湍流/喷泉运动。(4)CR光谱在星系中有很大的差异;某些特征可能来自局部结构而不是传输物理。(5)在LISM和分子云（或银河系位置）之间的CR电离率的系统变化自然出现，而无需调用替代源。(6)CNO核的丰度要求大部分CR加速发生在SNe的反向冲击形成时，而不是在OB风泡或SNe残余的Sedov-Taylor阶段。
We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV–TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-magnetohydrodynamics galaxy simulations with star formation and feedback. We utilize new numerical methods including terms often neglected in historical models, comparing Milky Way analogues with phenomenological scattering coefficients ν to Solar-neighbourhood [Local interstellar medium (LISM)] observations (spectra, B/C, e+/e−,,10Be/9Be, ionization, and γ-rays). We show it is possible to reproduce observations with simple single-power-law injection and scattering coefficients (scaling with rigidityR), similar to previous (non-dynamical) calculations. We also find: (1) The circumgalactic medium in realistic galaxies necessarily imposes ankpc CR scattering halo, influencing the required ν(R). (2) Increasing the normalization of ν(R) re-normalizes CR secondary spectra but also changes primary spectral slopes, owing to source distribution and loss effects. (3) Diffusive/turbulent reacceleration is unimportant and generally sub-dominant to gyroresonant/streaming losses, which are sub-dominant to adiabatic/convective terms dominated bykpc turbulent/fountain motions. (4) CR spectra vary considerably across galaxies; certain features can arise from local structure rather than transport physics. (5) Systematic variation in CR ionization rates between LISM and molecular clouds (or Galactic position) arises naturally without invoking alternative sources. (6) Abundances of CNO nuclei require most CR acceleration occurs around when reverse shocks form in SNe, not in OB wind bubbles or later Sedov–Taylor stages of SNe remnants.