Active Galactic Nuclei Part II: jets in AGN 3C 273 (Soldi et al. 2008) Anima6on: COSMOVISION / A. Marscher Volker Beckmann CNRS / IN2P3 Cargèse, May 25, 2016 Active Galactic Nuclei •  Active Galactic Nuclei (AGN) are efficient particle accelerators •  Jets (relativistic outflows) •  Winds (non-relativistic outflows) Credit: NASA / Ann Field (STScI) Credit: NASA / CXC / M. Weiss Jets in AGN Jets are real! Cygnus A; Carilli & Barthel (1996) 3C 273, Chandra Cen A, Fermi/LAT M87: Image courtesy of NRAO/AUI and Abdo et al. 2010 Y. Y. Kovalev, MPIfR and ASC Lebedev Centaurus A Jets appear single-sided and symmetric, visible (resolvable) from the radio to the X-ray (gamma-ray) domain Jets are ou*lows Anima1on: Lindfors et al. (2006), see Marc Türler’s website at the ISDC 3C 279 AGILE (>100 MeV), Giuliani et al. 2009 VHE MAGIC observa6on (~ TeV) Chandra X-ray image Jets in AGN •  Jets are ou*lows •  Super luminal mo6on observed (up to 40c) •  Geometric effect (Rees 1966): Mrk 421 Graphic: Beckmann & Shrader (2012) Inverse Compton 22 GHz VLBI map of 3C 279, showing apparent speed of 7.5c (Wehrle et al. 2001) Synchrotron emission •  Synchrotron emission is a strong indicator of a jet •  Fast moving, charged par6cle in magne6c field •  L (Z, B, γ, m) m /m = 1836 ! L is 3 10-7 lower for protons when p e assuming the same speed for electron and proton. Assuming same par6cle energy E (i.e. proton slower): L is lower by 9 10-14 for protons Graphic: Beckmann & Shrader (2012) Synchrotron emission in AGN jets is dominantly produced by electrons and/or positrons Lorentz factor: Protons are likely also to be accelerated, but do not contribute significantly to the synchrotron power Synchrotron emission •  Synchrotron emission depends on energy distribu6on of emikng par6cles •  Direct link between the slope p of the electron energy distribu6on and the slope α of the synchrotron spectrum (in the radio band): p = 2α + 1 •  infinite at low energies? •  Synchrotron self-absorp6on •  Synchrotron light reabsorbed by e- •  Most efficient close to cri6cal frequency of electron: Less chances to catch an electron at high E Spectrum: absorp6on coefficient (ν), B and electron popula6on isotropic… Graphic: Beckmann & Shrader (2012) Inverse Compton (IC) emission •  Rela6vis6c, charged par6cles (e.g. from plasma in jet) •  Dense photon field (e.g. from synchrotron or external field) •  Inverse Compton (IC) scauering •  quasi elas6c: Thomson scauering (E is the photon energy 1 befor the scauering, E aver the scauering) 2 ! Thomson Klein-Nishina correc6on •  Mul6ple IC scauerings possible Graphic: Beckmann & Shrader (2012) Beckmann & Shrader (2012); graphic by Marie-Luise Menzel Jets in AGN X-ray op1cal Mrk 421 γ-ray Synchrotron emission Inverse Compton Radio SED of Mrk 421 (Abdo et al. 2011, ApJ, 736, 131)