恒星形成星系的高能辐射
High-energy emission from star-forming galaxies
摘要：
采用高能电子和质子传输的对流-扩散模型，考虑所有相关的强子和轻子过程，通过详细的数值处理，可以确定星暴星系M82和NGC 253中这些粒子的稳态能量分布。电子分布直接归一化的同步辐射辐射从中央星爆区域，一个共同预期的理论关系，然后用于规范化的质子光谱在这一地区，和径向配置文件被假定为磁场。计算得到的电子和质子的辐射产额：预测的> 100 MeV和> 100 GeV通量与轨道费米望远镜和地面VERITAS和HESS切伦科夫望远镜测量的相应量一致。在星暴星系中心区域的宇宙射线能量密度，分别由非热同步辐射和中性π衰变辐射的射电和伽马射线测量结果推断，为U=O（100）eV/cm 3，也就是说，至少比银河系中心附近和其他恒星形成不太活跃的星系大一个数量级。这些非常不同的能量密度水平反映了两种环境中各自超新星速率的相似差异。然后预测了L（γ）~ SFR^（1.4）关系，与初步的观测证据一致。
英文摘要：
Adopting the convection-diffusion model for energetic electron and proton propagation, and accounting for all the relevant hadronic and leptonic processes, the steady-state energy distributions of these particles in the starburst galaxies M82 and NGC253 can be determined with a detailed numerical treatment. The electron distribution is directly normalized by the measured synchrotron radio emission from the central starburst region; a commonly expected theoretical relation is then used to normalize the proton spectrum in this region, and a radial profile is assumed for the magnetic field. The resulting radiative yields of electrons and protons are calculated: the predicted >100MeV and >100GeV fluxes are in agreement with the corresponding quantities measured with the orbiting Fermi telescope and the ground-based VERITAS and HESS Cherenkov telescopes. The cosmic-ray energy densities in central regions of starburst galaxies, as inferred from the radio and gamma-ray measurements of (respectively) non-thermal synchrotron and neutral-pion-decay emission, are U=O(100) eV/cm3, i.e. at least an order of magnitude larger than near the Galactic center and in other non-very-actively star-forming galaxies. These very different energy density levels reflect a similar disparity in the respective supernova rates in the two environments. A L(gamma) ~ SFR^(1.4) relationship is then predicted, in agreement with preliminary observational evidence.
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