Active Galactic Nuclei What are Active Galactic Nuclei

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

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 activity Questions.

AGN Properties ● Highly luminous: Lbol ~1042 – 1048 ergs s-1 ● Compact: size << 1 pc ● ● Broad-band continuum emission: d. L / 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

AGN Models Supermassive Black Hole: M ~ 106 – 109 Mo Accretion Powered: . 2 L ~ h. Mc Efficiency Accretion rate Eddington Luminosity: Frad = Fgrav LEdd~1. 3 x 1038(M/Mo) ergs/s Urry & Padovani 1998

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

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!

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

NGC 253 – starburst Chandra can resolve structures on 1 arcsec scale

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 21 st Century

X-ray Jets ● ● ● Many Chandra observations revealed Xray 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, B 20738+393 Relativistic motion at hundreds kpc distance from the quasar!

PKS 1127 -145 z=1. 187 Chandra HST/WFPC 2 ~300 kpc Siemiginowska et al 200

B 2 0738+313 z=0. 63 X-ray/Radio Siemiginowska et al 2003

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)

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

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

X-ray Absorption due to Ionized Gas close to the nucleus

MCG 6 -30 -15 Chandra/HETG OVII edge

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

High velocity outflow in PG 1211+143 Pounds et al 2003 Velocity of outflowing ionized gas based on the line broadening ~ 0. 09 -0. 1 c Mg XII Lya S XVI Lya Fe XXVI Lya

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

Zycki (2003)

A case for a broad line in MCG 6 -3015? ASCA Chandra Lee et al 2002 Fabian 2002

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

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

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

Extragalactic X-ray Background 0. 2 -400 ke. V Gilli 2003(astro-ph/0303115) DATA Making XRB Compton Thick Total Type 1 Thin Fabian 2003 (astro-ph/0304122)

Absorbing Column Density in CDFS Luminosity (2 -10) ke. V Redshift Gilli 2003

NGC 6240 Beppo. SAX IRAS 09104+4109 Obscured AGN * Large number of obscured sources! 3 C 294 A 18 * What is the evolution of obscured sources? * Why they have large absorbing columns? * What is their black hole mass distribtion? Are they less massive? Fabian (2003, astroph/0304122)

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 M 87, Sgr. A*, ● IC 1459 Perseus A Fabian 2001

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

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