标题： 活动星系核喷流底部云层穿透的伽马射线 显示英文标题

标题： Gamma rays from cloud penetration at the base of AGN jets

摘要： 致密且寒冷的云似乎充斥着活动星系核中心黑洞周围的宽线区。 这些云可能与活动星系核喷流基部相互作用，这可能产生观测上的后果。 我们想要研究由这些喷流-云相互作用产生的伽马射线辐射，并探讨在何种条件下这种辐射是可以被探测到的。 我们研究喷流-云相互作用的流体力学特性及由此产生的激波，并开发一个模型来计算由这些激波中加速的粒子所产生的发射的能谱分布。 我们在射电强活动星系核的背景下讨论我们的模型，并应用于两个代表性案例，即低光度的半人马座A和强大的3C 273。 喷流功率的一部分可以转化为伽马射线，这些伽马射线很可能是由同步自康普顿辐射主导的，并表现出典型的变异性时间尺度，与喷流中的云寿命相似，这比几小时更长。 许多云可以同时与喷流相互作用，导致通量显著高于单次相互作用，但随后变异性将被平滑。 喷流-云相互作用可能在非耀变体活动星系核中产生可探测的伽马射线，在邻近低光度源如Cen A中表现为瞬态，在FR II型强大天体的情况下则为稳态。 显示英文摘要

摘要： Dense and cold clouds seem to populate the broad line region surrounding the central black hole in AGNs. These clouds could interact with the AGN jet base and this could have observational consequences. We want to study the gamma-ray emission produced by these jet-cloud interactions, and explore under which conditions this radiation would be detectable. We investigate the hydrodynamical properties of jet-cloud interactions and the resulting shocks, and develop a model to compute the spectral energy distribution of the emission generated by the particles accelerated in these shocks. We discuss our model in the context of radio-loud AGNs, with applications to two representative cases, the low-luminous Centaurus A, and the powerful 3C 273. Some fraction of the jet power can be channelled to gamma-rays, which would be likely dominated by synchrotron self-Compton radiation, and show typical variability timescales similar to the cloud lifetime within the jet, which is longer than several hours. Many clouds can interact with the jet simultaneously leading to fluxes significantly higher than in one interaction, but then variability will be smoothed out. Jet-cloud interactions may produce detectable gamma-rays in non-blazar AGNs, of transient nature in nearby low-luminous sources like Cen A, and steady in the case of powerful objects of FR II type.