Flat Radio Sources

Almost every galaxy hosts a BH 99% are silent 1% are active 0.1% have jets

Radio lobes No lobes Powerful FRII radio-galaxy Weak FRI radio-galaxy Broad emission lines No or weak lines emission lines

Radio-galaxies & Blazars FSRQs= Flat Spectrum Radio Quasars, with broad lines BL Lacs= less powerful, no broad lines FR II poweful radio galaxy, with lobes FR I: weak radio galaxy, no lobes R s

Radio VLBIOptical HST Superluminal motion

Blazars: phenomenology

Synchro Inverse Compton (also possible hadronic models) Radio IR Opt UV X MeV GeV Blazars: Spectral Energy Distribution

Fossati et al. 1998; Donato et al The “blazar sequence” FSRQs BL Lacs LBL and HBL AGILE GLAST CT

Gamma-ray blazars Fermi HESS+ MAGIC EGRET: ~100 blazars Cherenkov: ~40 blazars (a few Radiogal) The Universe becomes opaque at z~0.1 at 1TeV at z~2 at 20 GeV

9 years of EGRET ( GeV) After 11 months: ~700 (blazars, FSRQsand BL Lacs in equal number) A few radiogalaxies 4 NLSy1 Starburst galaxies Fermi first light, 96 hrs of integration

Blazars: emission models

Coordinated variability at different Coordinated variability at different Mkn 421 TeV PDS MECS LECS

BL Lacs: low power, no lines

Tagliaferri et al. + MAGIC, 2008 TeV BL Lacs Ferm i 1 yr 5 

 ADAF? L< L Edd ?  No BLR No IR Torus Weak cooling Large 

Emission Models SSC model Simplest scenario: SSC model No external radiation

The simplest model   R Log  Log N(  )   n1 bb Log Log L( )   2 s B e   n2

The simplest model Log  Log N(  ) n1n1 n2n2 bb Log U syn ( ) + Log 11  ’ s Log Log L( )  22 s  22 C

The simplest model Log  Log N(  ) n1n1 n2n2 bb + “Klein-Nishina regime” h ’ s  b >m e c 2 Log L( ) Log  22 s   KN C Log Log U syn ( ) 11  ’ s

SSC model: constraining the parameters In the simplest version of the SSC model, all the parameters can be constrained by quantities available from observations: Model parameters: R B N o  b n 1 n 2  Observational parameters: s L s C L C t var  1  2 7 free parameters 7 observational quantities Tavecchio et al. 1998

K K2K2

   

FSQRs: high power, strong broad emission lines

SX 10 4 s Data: Fabian+ 2001

Torus ~1-10 pc BLR ~0.2 pc R BLR ~ L disk  U BLR = const 1/ 2 R Torus ~ L disk  U IR = const 1/ 2 L B ~ B 2 R 2  2 c = const  B~1/(R  )

Torus ~1-10 pc ? ? BLR ~0.2 pc

Importance of  -rays If blob too close to disk, or too compact, AND if emits  -rays, then many pairs If blob too large (too distant) t var too long Then: R diss ~ 1000 R S Energy transport in inner jet must be dissipationless

 b = 10 3  max = 10 4 R diss = 20R s  = 10 torus disk corona

The simplest model - 5 Log  Log N(  ) n1n1 n2n2 bb + Log Log U ext ( ) Broad line region, Disk o ’ o   Log Log F( )  22 s  22 C

B =  =  b = Ballo et al C 279 EC + SSC The simplest model - 6

Torus ~8 pc BLR ~0.3 pc CMB A text-book jet B propto 1/R n propto 1/R 2 M=10 9 M o L disk ~L Edd z=3

pc SX 10 5 s

2 2 1 pc

pc

pc

5 5 1 kpc

kpc

kpc

kpc 1 kpc 100 pc 10 pc 1 pc 0.1 pc 0 SX 10 5 s

kpc 1 kpc 100 pc 10 pc 1 pc 0.1 pc 0 SX 10 5 s Peak at ~ keV Hard X-rays and GeV: same component (t var ~0.5-1 day) Soft X-rays: contributions from larger regions, but within 10 pc (t var <2.5 months) 100 kpc

Fossati et al. 1998; Donato et al. 2001

By modeling, we find physical parameters in the comoving frame.  peak is the energy of electrons emitting at the peak of the SED EGRET blazars Ghisellini et al. 1998

Low power slow cooling large  peak Big power fast cooling small  peak

 -ray emission from non-blazar AGNs Only one non–blazar AGNs is known at VHE band: the radiogalaxy M87

Emission region? Large scale jet Stawarz et al Knot HST-1 (60 pc proj.) Stawarz et al Cheung et al Misaligned (20 deg) blazar Georganopoulos et al Lenain et al FT and GG 2008 BH horizon Neronov & Aharonian 2007 Rieger & Aharonian 2008

Core? Acciari et al. 2008

Ghisellini Tavecchio Chiaberge 2005 Tavecchio & Ghisellini 2008 spine layer

More seed photons for both   rel =  layer  spine (1-  layer  spine )  The spine sees an enhanced U rad coming from the layer  Also the layer sees an enhanced U rad coming from the spine The IC emission is enhanced wrt to the standard SSC model

BL Lac Radiogalaxy

Misaligned structured blazar jet FT and GG 2008

The End

Evidences for relativistic beaming Superluminal motions Level of Compton emission High brightness temperatures Gamma-ray emission/absorption (see below)

Radiogalaxy (FRI, FRII), SSRQ Blazar (BL Lac [no BL], FSRQ [BL] ) BH Broad Line Region Narrow Line Region Urry & Padovani 1995 “Unification scheme” Accretion flow/disk (T~1e4 K) Obscuring torus (hot dust) Blazar characteristics: - Compact radio core, flat or inverted spectrum - Extreme variability (amplitude and t) at all frequencies - High optical and radio polarization FSRQsbright broad ( km/s) emission lines FSRQs: bright broad ( km/s) emission lines often evidences for the “blue bump” (acc. disc) often evidences for the “blue bump” (acc. disc) BL Lacertae: weak (EW<5 Å) emission lines no signatures of accretion no signatures of accretion

The radio-loud zoo is large and complex Messy classification! FRI, FRII, NLRG, BLRG, FSRQ, OVV, HPQ, BL Lac objects … Idea: Jet emission is anisotropic (beaming): viewing angle + intrinsic jet (and AGN) power

Almost all galaxies contain a massive black hole 99% of them is (almost) silent (e.g. our Galaxy) 1% per cent is active (mostly radio-quiet AGNs): BH+accretion flow (disk): most of the emission in the UV-X-ray band 0.1% is radio loud: jets mostly visible in the radio e.g. Ferrarese & Ford 2004

FRII source: Cygnus A

FRI source: 3C31

VHE emission of M87 Light curve Spectrum t var ~ 2 days !

New problems: Ultra-rapid variability Aharonian et al H.E.S.S. Albert et al MAGIC Mkn 501 PKS

Observed time: (R 0 /c)  2 (1-  cos  ) ~ R 0 /c ! Rees 1978 for M87

t var =200 s In the standard scenario t var >r g /c = 1.4 M 9 h ! Conclusion: only a small portion of the jet (and/or BH horizon) is involved in the emission (e.g. Begelman, Fabian & Rees 2008)

Possible alternative: VHE emission from a fast, transient “needle” (Ghisellini & Tavecchio 2008) VHE emission dominated by IC from the needle (spine) scattering the radiation of the jet (layer) A different “flavour” of the spine-layer scenario

GG & FT 2008 Jet - needle

Suggested readings Black holes in galaxies: Ferrarese & Ford 2004, astro-ph/ BH in AGNs: Rees 1984, ARAA, 22, 471 Blandford 1990, Saas Fee Course 20 Krolik, “AGNs”, 1999, Princeton Univ. Press Beaming: Ghisellini 1999, astro-ph/ Unification schemes: Urry & Padovani 1995, PASP, 107, 803 Emission Mechanisms: Rybicki & Lightman, 1979, Wiley & Son Jets: Begelman, Blandford & Rees, 1984, Rev. Mod. Physics, 56, 255 de Young, The physics of extragal. radio sources, 2002, Univ. Chicago Press VHE emission: Aharonian, VHE cosmic gamma radiation, 2004, World Scientific SSC: Tavecchio, Maraschi Ghisellini, 1998, ApJ, 509, 608

Absorption of  -rays

In astrophysical environments  -rays are effectively absorbed through  -> e+  e- Photon-photon pair production in a nutshell    x1x1 x2x2 threshold Rule of thumb: In isotropic rad. fields, with declining spectra:

Internal opacity: limit on  Observations of gamma rays provide interesting limits on the minimum value of the Doppler factor E  = GeV h =5-50 eV (UV photons) Without any correction:  (x)=   R n(1/x) 1/x ~ (1/x)  ~ x   increasing with E (x=E/mc 2 ) where n(1/x) 1/x ~ L (1/x) / R 2  (100 GeV)>>1  -rays cannot escape!!

Taking into account relativistic motion: 1) Intrinsic energy of gamma-ray is lower: decreasing number density of target photons 2) Density of target soft photons also strongly decreases (lower luminosity, larger radius) e.g. Ghisellini & Dondi 1996 One can find:  ‘ (x)=  (x)/  4+2  Therefore :  (x) 1/(4+2  ) Typically  5 Internal opacity: limit on 

Absorption inside the BLR

Intergalactic absorption

For TeV blazars the parameters also depends on the intergalactic absorption correction (Stecker et al. 1992). Values of delta up to 50 are obtained (Krawczynski et al. 2002, Konopelko et al. 2003) The correction is uncertain: deconvolved TeV spectral shape can be used to discriminate between different possibilities  ntergalactic absorption Problem and opportunity at the same time!

Extragalactic background light EBL measurements Mazin & Raue 2007 Starlight Dust

The “  -ray horizon” Coppi & Aharonian 1997 Cen A M87 Mkn 501 3C 273 Mean free path

Aharonian et al. 2006: even with the lowest IR background the de-absorbed spectrum is very hard (photon index=1.5). Large EBL Medium EBL Minimum EBL

Katarzinski et al However, harder intrinsic spectra can be obtained assuming a power law electron distribution with a relatively large lower limit  min F ~ 1/3 The absolute limit is: Synchrotron SSC Below the corresponding freq. synchrotron and SSC spectra are very hard!

B B2B2 ~B (Klein Nishina

Jorstad et al. 2001

Superluminal motion

The relativistic Doppler factor   L=L’  4  ’   t=  t’/   1  cos  Special relat. Photon “compression”

 b (Klein Nishina) bb bb b2b2

Absorption inside the BLR - 2

Constraints from 3C279 Albert at al. 2008

VHE emission of FSRQs 3C 279, z=0.536 Albert at al. 2008

The future -2 New Cherenkov Telescope Arrays: CTA, Europe AGIS, USA

Observed time: (R 0 /c)  2 (1-  cos  ) ~ R 0 /c ! Rees 1978 for M87

3C 279 Spada et al. 2001

Mkn 421 Guetta et al. 2004