Blazars Gamma-ray sky Structure formation The Physics and Cosmology of TeV Blazars Christoph Pfrommer1 in collaboration with Avery E. Broderick, Phil Chang, Ewald Puchwein, Astrid Lamberts, Mohamad Shalaby, Volker Springel 1Heidelberg Institute for Theoretical Studies, Germany Jun 11, 2015 / Nonthermal Processes in Astrophysical Phenomena, Minneapolis Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Gamma-ray sky Structure formation Motivation A new link between high-energy astrophysics and cosmological structure formation Introduction to Blazars active galactic nuclei (AGN) propagating gamma rays plasma physics Cosmological Consequences unifying blazars with AGN gamma-ray background thermal history of the Universe Lyman-α forest formation of dwarf galaxies Christoph Pfrommer The Physics and Cosmology of TeV Blazars AGNs are among the most luminous sources in the universe → discovery of distant objects Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Active galactic nucleus (AGN) AGN: compact region at the center of a galaxy, which dominates the luminosity of its electromagnetic spectrum AGN emission is most likely caused by mass accretion onto a supermassive black hole and can also launch relativistic jets Centaurus A Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Active galactic nucleus at a cosmological distance AGN: compact region at the center of a galaxy, which dominates the luminosity of its electromagnetic spectrum AGN emission is most likely caused by mass accretion onto a supermassive black hole and can also launch relativistic jets AGNs are among the most luminous sources in the universe → discovery of distant objects Quasar 3C175 at z ' 0.8: jet extends 106 light years across Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Unified model of active galactic nuclei relativistic jet accretion disk dusty torus super−massive black hole Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Unified model of active galactic nuclei relativistic jet accretion disk dusty torus super−massive black hole Blazar: jet aligned with line-of-sight Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities TeV gamma-ray observations MAGIC VERITAS H.E.S.S. Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities The TeV gamma-ray sky There are several classes of TeV sources: Galactic - pulsars, BH binaries, supernova remnants Extragalactic - mostly blazars, two starburst galaxies Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Annihilation and pair production blazar e− TeV e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Annihilation and pair production blazar e− TeV e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Inverse Compton cascades cosmic microwave background, 10 −3 eV − TeV blazar GeV e e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Inverse Compton cascades cosmic microwave background, 10 −3 eV − TeV blazar GeV e e+ extragalactic backgroud light (infrared, eV) each TeV point source should also be a GeV point source! Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars – not seen! Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities What about the cascade emission? Every TeV source should be associated with a 1-100 GeV gamma-ray halo expected cascade TeV detections emission intrinsic spectra Neronov & Vovk (2010) Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities What about the cascade emission? Every TeV source should be associated with a 1-100 GeV gamma-ray halo – not seen! expected cascade TeV detections emission intrinsic spectra Fermi exclusion region Neronov & Vovk (2010) Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Inverse Compton cascades cosmic microwave background, 10 −3 eV − TeV blazar GeV e e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Extragalactic magnetic fields? pair deflection in intergalactic magnetic field blazar e− TeV GeV e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Extragalactic magnetic fields? pair deflection in intergalactic magnetic field blazar e− TeV GeV e+ extragalactic backgroud light (infrared, eV) GeV point source diluted weak "pair halo" stronger B−field implies more deflection and dilution, gamma−ray non−detection −Pfrommer primordial fields? Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Extragalactic magnetic fields? pair deflection in intergalactic magnetic field blazar e− TeV GeV e+ extragalactic backgroud light (infrared, eV) problem for unified AGN model: no increase in comoving blazar density with redshift allowed (as seen in other AGNs) since other− wise, extragalactic GeV background would be overproduced!Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities What else could happen? blazar e− TeV e+ extragalactic backgroud light (infrared, eV) Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Plasma instabilities intergalactic medium blazar e− TeV e+ pair plasma beam propagating through the intergalactic medium Pfrommer Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Plasma instabilities pair beam intergalactic medium (IGM) this configuration is unstable to plasma instabilities characteristic frequency and length scale of the problem: s 2 4πe ne c 8 ωp = , λp = ∼ 10 cm me ωp ρ¯(z=0) Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Two-stream instability consider wave-like perturbation in background plasma along the beam direction (Langmuir wave): initially homogeneous beam-e−: attractive (repulsive) force by potential maxima (minima) e− attain lowest velocity in potential minima → bunching up e+ attain lowest velocity in potential maxima → bunching up Φ + p p e− e − Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Two-stream instability consider wave-like perturbation in background plasma along the beam direction (Langmuir wave): beam-e+/e− couple in phase with the background perturbation: enhances background potential stronger forces on beam-e+/e− → positive feedback exponential wave-growth → instability e+ e+ Φ + p p e− e− e− e − Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Two-stream instability: momentum transfer particles with v & vphase: pair momentum → plasma waves → growing modes: instability particles with v . vphase: plasma wave momentum → pairs → Landau damping Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Oblique instability k oblique to v beam: real word perturbations don’t choose “easy” alignment = P all orientations oblique grows faster than two-stream: E-fields can easier deflect ultra-relativistic particles than change their parallel velocities (Nakar, Bret & Milosavljevic 2011) Bret (2009), Bret+ (2010) Christoph Pfrommer The Physics and Cosmology of TeV Blazars Blazars Active galactic nuclei Gamma-ray sky Propagating γ rays Structure formation Plasma instabilities Beam physics – growth rates excluded for collective consider a light beam plasma phenomena