Gamma rays from jets interacting with BLR clouds in blazars

Abstract

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 the $\gamma$-ray emission from blazars. 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 the $\gamma$-ray emission in blazars. 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 of $\gamma$-rays in the ambient photon field through pair creation. Jet-cloud interactions can lead to significant $\gamma$-ray fluxes in blazars with a broad-line region, 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 broad-line region; and 3) an increased observer luminosity due to Doppler boosting effects. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistent $\gamma$-ray emission from blazars or (ii) the broad-line region is far from spherical or the fraction of energy deposited in non-thermal electrons is small.

9 pages, 9 figures. Accepted for publication in A&A

References in corpus (31)

• Revisiting the Unified Model of Active Galactic Nuclei
• The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
• The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Canonical high power blazars
• The power of relativistic jets is larger than the luminosity of their accretion disks
• Reverberation Mapping of High-Luminosity Quasars: First Results
• The Fermi blazar sequence
• The Structure of the Broad Line Region in AGN: I. Reconstructed Velocity-Delay Maps
• What broad emission lines tell us about how active galactic nuclei work
• Simple analytical approximations for treatment of inverse Compton scattering of relativistic electrons in the black-body radiation field
• Fermi/LAT broad emission line blazars
• Absorption of 10--200 Gev Gamma Rays by Radiation from BLR in Blazars
• The spectrum of the Broad Line Region and the high-energy emission of powerful blazars
• On the origin of gamma rays in Fermi blazars: beyond the broad line region
• Rapid TeV variability in Blazars as result of Jet-Star Interaction
• The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
• Optical microvariability of EGRET blazars
• Gamma rays from cloud penetration at the base of AGN jets
• Radiation fields of disk, BLR and torus in quasars and blazars: implications for gamma-ray absorption
• Hadronic Production of TeV Gamma Ray Flares from Blazars
• Modeling Variable Emission Lines in AGNs: Method and Application to NGC 5548
• Scenarios for ultrafast gamma-ray variability in AGN
• On the Hadronic Beam Model for Gamma-ray Production in Blazars
• Interpretation of the flares of M87 at TeV energies in the cloud-jet interaction scenario
• Gamma-Gamma Absorption in the Broad Line Region Radiation Fields of Gamma-Ray Blazars
• Star-Jet Interactions and Gamma-Ray Outbursts from 3C454.3
• Gamma-ray variability from wind clumping in HMXBs with jets
• Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars
• Cloud ablation by a relativistic jet and the extended flare in CTA 102 in 2016 and 2017
• Coupling hydrodynamics and radiation calculations for star-jet interactions in AGN
• The impact of red giant/AGB winds on AGN jet propagation

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• Modeling the effects of clumpy winds in the high-energy light curves of γ-ray binaries
• Modelling the persistent low-state $\gamma$-ray emission of the PKS 1510-089 blazar with electromagnetic cascades initiated in hadronuclear interactions
• X-ray Spectral Variability as Probe of Multimessenger Emission in Blazar 5BZB J0630-24064
• The ablation of gas clouds by blazar jets
• Super-Accreting Active Galactic Nuclei as Neutrino Sources
• Multi-wavelength observations of the Blazar 4C +28.07
• Non-thermal emission from fall-back clouds in the Broad-Line Region of Active Galactic Nuclei