基于贝叶斯分析的空间相关cosmic-ray传播模型约束
Constraints on the spatially dependent cosmic-ray propagation model from Bayesian Analysis
摘要：
初级和次级宇宙射线（CR）的能谱一般在几百GeV处硬化，这可以通过传播效应自然地解释。我们采用了一个空间依赖的CR传播模型来拟合光谱硬化，其中一个慢扩散盘（SDD）被假定在银河系平面附近。我们的目标是约束的传播参数的贝叶斯参数估计的基础上马尔可夫链蒙特卡罗抽样算法。在贝叶斯分析中采用了最新的碳谱和B/C比的精确测量。还包括$\rm{^{10}Be/^{9}Be}$和Be/B比率以破坏参数简并。拟合结果表明，各参数均得到了较好的约束。特别是SDD的厚度限制在银道面上下0.4- 0.5kpc，这可能是同类工作中对慢扩散区的最佳限制。SDD模型预测的CR各向异性的$\bar{p}/p$比和幅度与观测结果一致，而预测的高能电子和正电子通量分别略低于观测值和显著低于观测值，表明额外源的必要性。
英文摘要：
The energy spectra of primary and secondary cosmic rays (CR) generally harden at several hundreds of GeV, which can be naturally interpreted by propagation effects. We adopt a spatially dependent CR propagation model to fit the spectral hardening, where a slow-diffusion disk (SDD) is assumed near the Galactic plane. We aim to constrain the propagation parameters with the Bayesian parameter estimation based on a Markov chain Monte Carlo sampling algorithm. The latest precise measurements of carbon spectrum and B/C ratio are adopted in the Bayesian analysis. The $\rm{^{10}Be/^{9}Be}$ and Be/B ratios are also included to break parameter degeneracies. The fitting result shows that all the parameters are well constrained. Especially, the thickness of the SDD is limited to 0.4-0.5 kpc above and below the Galactic plane, which could be the best constraint for the slow-diffusion region among similar works. The $\bar{p}/p$ ratio and amplitude of CR anisotropy predicted by the SDD model are consistent with the observations, while the predicted high-energy electron and positron fluxes are slightly and significantly lower than the observations, respectively, indicating the necessity of extra sources.
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