标题： 伽马射线辐射来自星系中光谱分辨的宇宙射线 显示英文标题

标题： Gamma-ray emission from spectrally resolved cosmic rays in galaxies

摘要： 宇宙射线（CRs）在附近星系的星际介质（ISM）中无处不在，但它们的许多特性并未得到很好的约束。 伽马射线观测在这方面提供了一个强大的工具，使我们能够约束CR质子与ISM的相互作用及其传输特性。 为了更好地理解观测特征与CR物理之间的联系，我们使用了一系列使用光谱解析CR传输的孤立星系的磁流体动力学（MHD）AREPO模拟，每个计算单元中都进行了光谱解析的CR传输，随后使用CRAYON+（Cosmic RAY emissiON）代码计算伽马射线发射。 在我们模拟的每个晕中，对CR能量依赖的空间扩散进行建模，与“灰色”稳态模型预测相比，会导致高能（约100 GeV）伽马射线分布更广，这在相应的发射图和径向剖面中尤其明显。 尽管如此，总伽马射线谱通常可以很好地由稳态模型近似，尽管恢复相同的光谱指数通常需要对扩散系数的能量依赖性进行轻微的变化。 我们的模拟再现了附近形成恒星的星系的观测光谱指数和伽马射线谱，并且也与近期对远红外-伽马射线关系的观测相匹配。 然而，我们发现与灰色模拟相比，光谱解析模型在较低恒星形成率下产生的光度略小。 我们的工作强调了对光谱解析CR传输进行建模的重要性，以准确预测空间解析的高能伽马射线发射，这将由即将推出的切连科夫望远镜阵列观测站进行探测。 显示英文摘要

摘要： Cosmic rays (CRs) are ubiquitous in the interstellar medium (ISM) of nearby galaxies, but many of their properties are not well-constrained. Gamma-ray observations provide a powerful tool in this respect, allowing us to constrain both the interaction of CR protons with the ISM and their transport properties. To help better understand the link between observational signatures and CR physics, we use a series of magneto-hydrodynamical (MHD) AREPO simulations of isolated galaxies performed using spectrally-resolved CR transport in every computational cell, with subsequent gamma-ray emission calculated using the CRAYON+ (Cosmic RAY emissiON) code. In each of our simulated halos, modelling the energy-dependent spatial diffusion of CRs leads to a more extended distribution of high-energy (~100 GeV) gamma rays compared to that predicted by a 'grey' steady-state model, which is especially visible in the corresponding emission maps and radial profiles. Despite this, the total gamma-ray spectra can often be well approximated by the steady-state model, although recovering the same spectral index typically requires a minor variation of the energy dependence of the diffusion coefficient. Our simulations reproduce the observed spectral indices and gamma-ray spectra of nearby star-forming galaxies and also match recent observations of the far infrared--gamma-ray relation. We find, however, that the spectrally resolved model yields marginally smaller luminosities for lower star formation rates compared to grey simulations of CRs. Our work highlights the importance of modelling spectrally resolved CR transport for an accurate prediction of spatially resolved high-energy gamma-ray emission, as will be probed by the upcoming Cherenkov Telescope Array observatory.