Flat Radio SourcesFlat Radio Sources

Almost every galaxy hosts a BHAlmost every galaxy hosts a BH

99% are silent99% are silent

1% are active1% are active

0.1% have jets0.1% have jets

RadiRadio o lobelobess

No No lobelobess

Powerful FRII Powerful FRII radio-galaxyradio-galaxy

Weak FRI Weak FRI radio-radio-galaxygalaxy

Broad emission lines

No or weak lines emission lines

Radio-galaxies & BlazarsRadio-galaxies & Blazars

FSRQs= Flat Spectrum FSRQs= Flat Spectrum Radio Quasars, Radio Quasars, with broad with broad lineslines

BL Lacs= less BL Lacs= less powerful, powerful, no broad no broad lineslines

FR II poweful radio FR II poweful radio galaxy, galaxy, with lobeswith lobes

FR I: weak radio FR I: weak radio galaxy, galaxy, no lobesno lobes

101022-10-103 3 RRss

Radio VLBI Optical HSTSuperluminal motion

Blazars: phenomenologyBlazars: phenomenology

SynchrSynchroo

Inverse Inverse ComptonCompton(also possible(also possiblehadronic hadronic models)models)

Radio IR Opt UV X MeV Radio IR Opt UV X MeV GeV GeV

Blazars: Spectral Energy DistributionBlazars: Spectral Energy Distribution

Fossati

et

al.

1998;

Don

ato

et

al.

Fossati

et

al.

1998;

Don

ato

et

al.

2001

2001

TheThe “blazar“blazar sequence”sequence”FSRQs

BL LacsBL LacsLBLLBL and and HBLHBL

AGILE AGILE GLASTGLAST

CTCT

Gamma-ray Gamma-ray blazarsblazars

FermiFermi

HESS+ HESS+ MAGICMAGIC

EGRET: ~100 blazarsEGRET: ~100 blazars

Cherenkov: ~40 blazars (a few Cherenkov: ~40 blazars (a few Radiogal)Radiogal)

The Universe The Universe becomes becomes opaque at opaque at z~0.1 at 1TeV z~0.1 at 1TeV at z~2 at 20 at z~2 at 20 GeVGeV

9 years of EGRET (0.1-10 GeV)

After 11 months:~700 (blazars, FSRQsand BL Lacs in equal number)A few radiogalaxies4 NLSy1Starburst galaxies

Fermi first light, 96 hrs of integration

Blazars: emission modelsBlazars: emission models

Coordinated variability at Coordinated variability at different different

Mkn 421Mkn 421

TeV

PDS

MECS

LECS

BL Lacs: BL Lacs: low power, no low power, no

lineslines

Tagliaferri et al. + MAGIC, Tagliaferri et al. + MAGIC, 20082008

TeV B

L

TeV B

L

Lacs

Lacs

Fermi 1 yr 5

ADAF? L< 10ADAF? L< 10-3-3 L LEddEdd??

No BLR No BLR No IR TorusNo IR Torus

Weak Weak cooling cooling

Large Large

Emission ModelsEmission Models

Simplest scenario: SSC model SSC model

No external radiation

The simplest modelThe simplest model

RR

Log

Log N()

n1

b

Log

Log L()

2

s

BB

een2

The simplest modelThe simplest model

Log

Log N()

n1

n2

b

Log Usyn()

+Log

1

’ s

Log

Log L()

2

s

2

C

The simplest modelThe simplest model

Log

Log N()

n1

n2

b +

““Klein-Nishina regime”Klein-Nishina regime”h h ’ ’ s s bb >m >meecc22

Log L()

Log

2

s

KN

C

Log

Log Usyn()

1

’ s

SSC model: constraining the parametersIn the simplest version of the SSC model, all the parameters can be constrained by quantities available from observations:

Model parameters: R B No b n1 n2

Observational parameters: s Ls C LC tvar 1 2

7 free parameters

7 observational quantities

Tavecchio et al. 1998

K

K2

FSQRs: FSQRs: high power, high power, strong broad strong broad

emission linesemission lines

SX 104 s

Data: Fabian+ Data: Fabian+ 20012001

Torus ~1-10 Torus ~1-10 pcpc

BLR ~0.2 BLR ~0.2 pcpc

RRBLRBLR ~ L ~ Ldisk disk

UUBLRBLR= =

constconst

1/1/22

RRTorusTorus~ L~ Ldisk disk

UUIRIR= const= const

1/1/22

LL BB ~

B ~

B22 RR

22 22 cc = co

nst

= const

B~1/(R

B~1/(R))

Torus ~1-10 Torus ~1-10 pcpc ??

??BLR ~0.2 BLR ~0.2 pcpc

Importance Importance

of of -rays-rays

If blob too close to disk, or too If blob too close to disk, or too compact, AND if emits compact, AND if emits -rays, -rays, then many pairsthen many pairs

If blob too large (too distant) tIf blob too large (too distant) tvarvar

too longtoo long

Then: RThen: Rdissdiss ~ 1000 R ~ 1000 RSS

Energy transport in inner Energy transport in inner jet must be jet must be

dissipationlessdissipationless

b b = 10= 1033

maxmax= 10= 1044 RRdissdiss= =

20R20Rs s

= = 1010

torustorus

diskdisk

coronacorona

The simplest model - 5

Log

Log N()

n1

n2

b +Log

Log Uext() Broad line region,Disk

o

’o

Log

Log F()

2

s

2

C

B = 0.6 - 0.5 = 17.8 - 12.3 b = 550 - 600

Ballo

et

al. 2

002

3C 2793C 279EC + SSCEC + SSC

The simplest model - The simplest model - 66

Torus ~8 pcTorus ~8 pc

BLR ~0.3 BLR ~0.3 pcpc

CMBCMB

A text-book jetA text-book jet

• B propto 1/R

• n propto 1/R2

• M=109Mo

• Ldisk~LEdd

• z=3

11

11

0.1 pc0.1 pc

SX 105 s

22

22

1 pc1 pc

33

33

10 pc10 pc

44

44

100 100 pcpc

55

55

1 kpc1 kpc

6666

10 10 kpckpc

77

77

100 100 kpckpc

55

66

44

33

22

11

77100 100 kpckpc10 10 kpckpc

1 kpc1 kpc

100 100 pcpc

10 pc10 pc

1 pc1 pc

0.1 pc0.1 pc

00

SX 105 s

55

66

44

33

22

11

77

10 10 kpckpc

1 kpc1 kpc

100 100 pcpc

10 pc10 pc

1 pc1 pc

0.1 pc0.1 pc

00

SX 105 s

Peak at ~ 100-500 keVPeak at ~ 100-500 keV

Hard X-rays and GeV: same Hard X-rays and GeV: same component (tcomponent (tvarvar~0.5-1 day)~0.5-1 day)

Soft X-rays: contributions Soft X-rays: contributions from larger regions, but from larger regions, but within 10 pc (twithin 10 pc (tvarvar<2.5 <2.5

months)months)

100 100 kpckpc

Fossati

et

al.

1998;

Don

ato

et

al.

Fossati

et

al.

1998;

Don

ato

et

al.

2001

2001

By By modeling, modeling, we find we find physical physical parameters parameters in the in the comoving comoving frame.frame.

peakpeak is the is the

energy of energy of electrons electrons emitting at emitting at the peak of the peak of the SEDthe SED

EGRET EGRET blazarsblazars

Ghisellini et al. 1998

Low power slow cooling large peak

Big power Big power fast fast cooling cooling small small peakpeak

-ray emission from non-blazar AGNs-ray emission from non-blazar AGNs

Only one non–blazar AGNs is known at VHE band: the radiogalaxy M87

Emission region?Emission region?

Large scale jetLarge scale jetStawarz et al. 2003

Knot HST-1 (60 pc proj.)Knot HST-1 (60 pc proj.)Stawarz et al. 2006Cheung et al. 2007

Misaligned (20 deg) blazarMisaligned (20 deg) blazarGeorganopoulos et al. 2005Lenain et al. 2007FT and GG 2008

BH horizonBH horizonNeronov & Aharonian 2007Rieger & Aharonian 2008

Core?Core?

Acc

iari

et

al.

2008

Ghisellini Tavecchio Chiaberge Ghisellini Tavecchio Chiaberge 20052005

Tavecchio & Ghisellini 2008Tavecchio & Ghisellini 2008

spinspin

ee

layelayerr

More seed photons for bothMore seed photons for both

rel= layerspine(1-layerspine)

The spine sees an enhanced Urad coming from the layer

Also the layer sees an enhanced Urad coming from the spine

The IC emission is enhanced wrt to the standard SSC model

BL LacBL Lac

Radiogalaxy

Misaligned structured blazar Misaligned structured blazar jetjet

FT a

nd

GG

2008

FT a

nd

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:Blazar characteristics:

- Compact radio core, flat or inverted spectrum- Extreme variability (amplitude and t) at all frequencies- High optical and radio polarization

FSRQsFSRQs: bright broad (10bright broad (1033-10-1044 km/s) emission lines 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 BL Lacertae: weak (EW<5 ÅÅ) emission lines) emission lines no signatures of accretionno signatures of accretion

The radio-loudThe radio-loud zoo zoo is large and complexis large and complex

Messy classification!Messy classification! FRI, FRII, NLRG, BLRG,FRI, FRII, NLRG, BLRG,FSRQ, OVV, HPQ, BL Lac objectsFSRQ, OVV, HPQ, BL Lac objects … …

Idea:Idea:

Jet emission is anisotropic (beaming): viewing angleJet emission is anisotropic (beaming): viewing angle++

intrinsic jet (and AGN) powerintrinsic jet (and AGN) power

Almost all galaxies contain a massive black hole Almost all galaxies contain a massive black hole

99% of them is (almost) silent (e.g. our Galaxy)99% of them is (almost) silent (e.g. our Galaxy)

1% per cent is active (mostly 1% per cent is active (mostly radio-quietradio-quiet AGNs): AGNs):

BH+accretion flow (disk): BH+accretion flow (disk): most of the emission in the UV-X-ray bandmost of the emission in the UV-X-ray band

0.1% is 0.1% is radio loudradio loud: jets mostly visible in the radio: jets mostly visible in the radio

e.g. Ferrarese & Ford 2004

FRII source: Cygnus A

FRI source: 3C31

VHE emission of M87VHE emission of M87

Light curveLight curve

SpectrumSpectrum

t var ~ 2 days !

New problems: Ultra-rapid New problems: Ultra-rapid variabilityvariability

Aharonian et al. 2007 - H.E.S.S.Aharonian et al. 2007 - H.E.S.S.

Albert et al. 2007 - MAGICAlbert et al. 2007 - MAGIC

Mkn 501Mkn 501

PKS 2155-304PKS 2155-304

Observed time: (RObserved time: (R00/c)/c)22(1-(1-coscos) ~ R) ~ R00/c /c

!!

Rees 1978 Rees 1978 for M87for M87

tvar =200 s

In the standard scenario tvar>rg/c = 1.4 M9 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 2008GG & FT 2008

JetJet - - needleneedle

Suggested readings Black holes in galaxies: Ferrarese & Ford 2004, astro-ph/0411247

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/9905181

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 Absorption of -rays-rays

In astrophysical environments -rays are effectively absorbed through

-> e+ e-

Photon-photon pair production in a nutshellPhoton-photon pair production in a nutshell

x1

x2

threshold

Rule of thumb:

In isotropic rad. fields, with declining spectra:

Internal opacity: limit on Internal opacity: limit on Observations of gamma rays provide interesting limits on the minimum value of the Doppler factor

E=10-100 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/mc2)where n(1/x) 1/x ~ L (1/x) / R2

(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 Typically 55

Internal opacity: limit on Internal opacity: limit on

Absorption inside the BLR Absorption inside the BLR

Intergalactic absorption

For TeV blazars the parameters also dependson 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 discriminatebetween 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 &

Aharo

nia

n 1

997

Cen ACen A

M87M87

Mkn 501Mkn 501

3C 2733C 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 Large EBLEBL MediuMediu

mEBLmEBLMinimuMinimumEBLmEBL

Kata

rzin

ski et

al. 2

00

6

However, harder intrinsic spectra can be obtained assuming a power lawelectron distribution with a relatively large lower limit min

F ~ 1/3

The absolute limit is:

Synchrotron

SSC

Below the corresponding freq.synchrotron and SSC spectraare very hard!

B

B2

~B (Klein Nishina

Jors

tad

et

al.

2001

Superluminal motion

The relativistic Doppler factor

L=L’4

’t=t’/

1

coscos

Special relat.

Photon “compression”

b (Klein Nishina)

b

b

b2

Absorption inside the BLR - 2Absorption 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 -2The future -2

New Cherenkov Telescope Arrays:New Cherenkov Telescope Arrays:

CTA, Europe

AGIS, USA

Observed time: (RObserved time: (R00/c)/c)22(1-(1-coscos) ~ R) ~ R00/c /c

!!

Rees 1978 Rees 1978 for M87for M87

3C 279 Spada et al. 20013C 279 Spada et al. 2001

Mkn

421 G

uett

a e

t al.

2004

Mkn

421 G

uett

a e

t al.

2004