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标题：Gamma rays from jets interacting with BLR clouds in blazars
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作者：S. del Palacio ; V. Bosch-Ramon ; G. E. Romero 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：623
DOI：10.1051/0004-6361/201834231
语种：English
出版社：EDP Sciences
摘要：Context. The innermost parts of powerful jets in active galactic nuclei are surrounded by dense, high-velocity clouds from the broad-line region, which may penetrate into the jet and lead to the formation of a strong shock. Such jet-cloud interactions are expected to have measurable effects on theγ-ray emission from blazars.Aims. We characterise the dynamics of a typical cloud-jet interaction scenario, and the evolution of its radiative output in the 0.1–30 GeV energy range, to assess to what extent these interactions can contribute to theγ-ray emission in blazars.Methods. We use semi-analytical descriptions of the jet-cloud dynamics, taking into account the expansion of the cloud inside the jet and its acceleration. Assuming that electrons are accelerated in the interaction and making use of the hydrodynamical information, we then compute the high-energy radiation from the cloud, including the absorption ofγ-rays in the ambient photon field through pair creation.Results. Jet-cloud interactions can lead to significantγ-ray fluxes in blazars with a broad-line region (BLR), in particular when the cloud expansion and acceleration inside the jet are taken into account. This is caused by 1) the increased shocked area in the jet, which leads to an increase in the energy budget for the non-thermal emission; 2) a more efficient inverse Compton cooling with the boosted photon field of the BLR; and 3) an increased observer luminosity due to Doppler boosting effects.Conclusions. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistentγ-ray emission from blazars or (ii) the BLR is far from spherical or the fraction of energy deposited in non-thermal electrons is small.
关键词：engamma rays: galaxiesgalaxies: activeradiation mechanisms: non-thermal