The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have hot accretion flows where thermal electrons naturally emit soft gamma rays via Comptonization of their synchrotron photons. Protons there can be accelerated via turbulence or reconnection, producing high-energy neutrinos via hadronic interactions. We demonstrate that our model can reproduce the gamma-ray and neutrino data. Combined with a contribution by hot coronae in luminous active galactic nuclei, these accretion flows can explain the keV – MeV photon and TeV – PeV neutrino backgrounds. This scenario can account for the MeV background without non-thermal electrons, suggesting a higher transition energy from the thermal to nonthermal Universe than expected. Our model is consistent with X-ray data of nearby objects, and testable by future MeV gamma-ray and high-energy neutrino detectors.

宇宙充满了 MeV 伽马射线和 PeV 中微子的漫射背景，其来源不明。在这里，我们提出了一个可以同时考虑两种背景的场景。低亮度活动星系核具有热吸积流，其中热电子通过其同步加速器光子的康普顿化自然发射软伽马射线。那里的质子可以通过湍流或重联加速，通过强子相互作用产生高能中微子。我们证明我们的模型可以再现伽马射线和中微子数据。结合发光活跃星系核中热日冕的贡献，这些吸积流可以解释 keV – MeV 光子和 TeV – PeV 中微子背景。这种情况可以解释没有非热电子的 MeV 背景，表明从热宇宙到非热宇宙的过渡能量比预期的要高。我们的模型与附近物体的 X 射线数据一致，并且可以通过未来的 MeV 伽马射线和高能中微子探测器进行测试。