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Active Galactic Nuclei What are Active Galactic Nuclei and Why Does Anyone Care? Julian Krolik

Aneta Siemiginowska Harvard-Smithsonian Center for Astrophysics Chandra X-ray Center. Active Galactic Nuclei What are Active Galactic Nuclei and Why Does Anyone Care? Julian Krolik. Outline. AGN models. What have we learned from Chandra and XMM? X-ray Jets Absorbers and Outflows

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Active Galactic Nuclei What are Active Galactic Nuclei and Why Does Anyone Care? Julian Krolik

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  1. Aneta Siemiginowska Harvard-Smithsonian Center for Astrophysics Chandra X-ray Center Active Galactic NucleiWhat are Active Galactic Nucleiand Why Does Anyone Care? Julian Krolik

  2. Outline • AGN models. • What have we learned from Chandra and XMM? • X-ray Jets • Absorbers and Outflows • Emission Lines • Deep Imaging and X-ray background • Obscured AGN • AGN activity • Questions.

  3. AGN Properties • Highly luminous: Lbol ~1042 – 1048ergs s-1 • Compact: size << 1pc • Broad-band continuum emission: dL / dlog n = const. From IR to X-rays and g-rays • Variable: stronger variations on smaller timescales at shorter wavelengths • Weakly polarized: 1% linear polarization • Radio emission: in some sources extended

  4. AGN Models SupermassiveBlack Hole: M ~ 106 – 109 Mo Accretion Powered: L ~ hMc2 . Accretion rate Efficiency Eddington Luminosity:Frad = Fgrav LEdd~1.3 x 1038(M/Mo) ergs/s Urry & Padovani 1998

  5. 3D Vision Elvis 2000 Top View Side – NAL Side – BAL

  6. What X-rays can tell us? • Thermal emission from hot gas: 105-107 K => hot gas is there! • Non-thermal emission: synchrotron, Comptonization => relativistic plasma!

  7. What X-rays can tell us? • X-ray emission regions: • Nucleus – unresolved component • Extended emission on different scales: parsec to hundreds kpc • Jets and radio lobes • Absorption properties: • Amount of absorbing material • Outflow/Inflow velocity • Cold/Warm absorbers • IonizationState • Abundance • Variability: • Scale/Size of the emitting and reprocessing regions

  8. NGC253 – starburst Chandra can resolve structures on 1arcsec scale

  9. Low scattering wings of the Chandra PSF => crucial for high dynamic range observations when looking at faint structures in the vicinity of strong sources => discovery of X-ray jets Discoveries happen even in 21st Century

  10. X-ray Jets • Many Chandra observations revealed X-ray jets associated with quasars: => jets are common phenomena. • Some jets were discovered in quasars where there was no previously known radio jet emission. Examples: PKS 1127-145, B20738+393 • Relativistic motion at hundreds kpc distance from the quasar!

  11. PKS 1127-145 z=1.187 Chandra HST/WFPC2 ~300 kpc Siemiginowska et al 2002

  12. B2 0738+313 z=0.63 X-ray/Radio Radio Siemiginowska et al 2003

  13. Jet Models • Comparison of X-ray, optical and radio data rules out thermal emission, SSC and simple direct synchrotron emission as primary source of the X-ray emission. • Inverse Compton scattering of Cosmic Microwave Background (IC/CMB) photons on relativistic jet electrons can describe the observations: => Required bulk motion Lorentz factors are higher for lower redshift quasar: G bulk ~10 vs. G bulk~ 2-3 • Are higher redshift quasars more likely to have X-ray jets? (Dan Schwartz Chandra project)

  14. Absorbers and Outflows Optical/UV Absorption due to IGM => Studies of Matter in the Universe Pettini 2003 Lya Forest Damped Lya

  15. X-ray Absorption: IGM HRC/LETG PKS 2155-304 Absorption Lines => due to WHIM T~106 K Nicastro et al 2002

  16. X-ray Absorption due to Ionized Gasclose to the nucleus

  17. MCG 6-30-15 Chandra/HETG OVII edge

  18. XMM-Newton/RGS MCG 6-30-15 Mkn 766 OVII and OVIII broad emission lines Emission or Absorption?

  19. High velocity outflow in PG 1211+143 Pounds et al 2003 Velocity of outflowing ionized gas based on the line broadening ~ 0.09-0.1c Mg XIILya S XVILya Fe XXVI Lya

  20. Emission Lines • Originate in the nucleus: • Accreting matter • Relativistic broadening – Fe -line • BLR clouds • Originate in the hot gas away from the nucleus – NLR in Syfert 2

  21. Zycki (2003)

  22. A case for a broad line in MCG 6-30-15? ASCA Chandra Lee et al 2002 Fabian 2002

  23. XMM- Newton Observations of Fe-line in Type 1 AGN MCG 6-30-15 XMM-Newton EPIC-PN Reeves 2002 (astro-ph/0211381)

  24. Deep X-ray Imaging • Deep Chandra and XMM observations: Gilli 2003 (astro-ph/0303115)

  25. Source Counts: Log N – log S Gilli 2003(astro-ph/0303115)

  26. Extragalactic X-ray Background 0.2-400 keV DATA Making XRB Gilli 2003(astro-ph/0303115) Compton Thick Total Type 1 Thin Fabian 2003 (astro-ph/0304122)

  27. Absorbing Column Density in CDFS Absorbing Column Redshift Luminosity (2-10) keV Gilli 2003

  28. Obscured AGN NGC 6240 BeppoSAX IRAS 09104+4109 * Large number of obscured sources! * What is the evolution of obscured sources? * Why they have large absorbing columns? * What is their black hole mass distribtion? Are they less massive? 3C294 A18 Fabian (2003, astro-ph/0304122)

  29. AGN Activity • Is the AGN always on? Or its activity is intermittent? • AGN in clusters => evidence for the past activity in forms of buoyant bubbles? • Low Luminosity AGN M87, SgrA*, IC1459 Perseus A Fabian 2001

  30. Galactic Center => was our Galaxy active in the past? Low Mass BH ~106 Mo Baganoff 2003

  31. Summary • AGN models • X-ray Jets • Absorption vs. Emission • Source counts and obscured AGN • AGN activity

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