On the Physics of Gamma-ray Emitting AGN in the Fermi Era Anita Reimer (Innsbruck University) 5thFermi Symposium, Nagoya, October 2014 Active Galactic Nuclei (AGN) -- a schematic view -- Blazar NLR Jet BLR Black Hole accretion dust torus disk Cen A 1.4GHz (orange), optical (grey), cartoon of a radio-loud AGN -rays (purple) Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 Three corner marks A. AGN AS A POPULATION AND THE BLAZAR PHENOMENON Won’t address here; see talks by Yoshiyuki Inoue, Markus Ackermann, Marco Ajello, Elisabetta Cavazzuti, Benoit Lott,… B. THE PHYSICS OF GAMMA-RAY EMITTING AGN Won’t address misaligned AGN (see talks by Y. Fukuzawa, I. Edahiro, E. Meyer, K. Hada, J. Sitarek) or NLSy1 (see posters by F. D’Ammando, H. Shirakawa) C. AGN AS A TOOL Won’t address here; see poster by Alberto Dominguez on EBL Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 Outline I Introduction II Models & diagnostics adressing open questions 1. ‘Crisis‘ on the location of the HE emission zone 2. On the jet composition 3. Diagnosing particle injection III Conclusions Jets of Active Galactic Nuclei: open questions Blazar Radio galaxy Jet composition? Energy [rel./cold leptons & transport? hadrons, B-fields & their properties] -ray Energy production: conversion? Where? How? Jet formation? [from: Urry & Padovani 1995] Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 Blazar -ray emission is beamed Opacity (-> e+e-) argument: • broad band high energy radiation with • high luminosity L • from a compact region R ≤ cT var -pair production opacity  = n  R ≈ n  R with n ≈ L / (4cR2E)   T photon density  ≈  L / (4c2 E T ) with E·E > (m c2)2 threshold condition  T var  e Transparency requires  « 1.  BUT: for many blazars one finds:  ≈ 100 L E-1 T-1 »1  46 MeV 1hr Solution [Rees 1966]: –ray emission from jet, beamed! e.g., for blob geometry: L ≈ D4·L’ ≈ 4c3D6·u’·T2 var Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 Non-thermal Emission Processes in AGN Jets: n Leptons   BB SSC syn ECD ECC e-/e+ ,  ,  e e,min e,max Location of the -ray emitting region -> implications for dominating target photon field for particle-photon interactions u’ CMB [Murase etal 2014] [Tavecchio etal 2013] Jet-frame densities of blazar target photon fields along the ‚blazar sequence‘ => Nature (& frequency) of dominating external target photon field in jet frame depends on distance from the central engine Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 -ray emitting region inside the BLR? -> explanation of spectral features(e.g.,‘GeV-break‘ measured in bright LSPs): • -absorption on H and HeII Ly continuum as possible explanation of ‘GeV-break’ [Poutanen&Stern’10, Stern&Poutanen‘11, ‘14] [Poutanen&Stern‘14] • ‘GeV-break’ as superposition of Compton-scattered accretion disk and BLR target radiation fields [Finke & Dermer 2010, Hunger & Reimer 2014] • EC off BLR photons by curved e-distribution [Cerrutietal2013, Hunger & Reimer 2014] -> rapid variability points to a location at small distances to the central engine [Finke&Dermer‘10] Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014 -ray emitting region outside the BLR? • -opacity arguments for >10GeV photon detections of luminous FSRQs (e.g., PKS 1222+216 [Nalewajko etal 2012], PKS B1424-418 [Tavecchio etal 2013]; BUT: [Lei & Wang 2013] • Change of optical polarization correlated with -ray flare (e.g., 3C 279 [Abdo etal 2010], PKS 1510-089 [Marscher etal 2010], PMNJ0948+0022 [Itoh etal 2013], ....) ->event duration constrains location of emission region: R ~ 22ct /(1+z) diss var • Within one-zone leptonic scenario large  / + large CD HE LE [Tavecchio etal 2013, Pacciani etal 2014] • Proposed location of the -ray emitting region in HSP-FSRQs? [Ghisellini etal 2013]  Problem: How to explain rapid (min scale!) variability in these sources? Anita Reimer, Innsbruck University 5th Fermi Symposium, Nagoya, Oct. 2014