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Flat Radio Sources. Almost every galaxy hosts a BH. 99% are silent 1% are active 0.1% have jets. No lobes. Radio lobes. Broad emission lines. No or weak lines emission lines. Weak FRI radio-galaxy. Powerful FRII radio-galaxy. Radio-galaxies & Blazars.

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Flat Radio Sources

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Flat Radio Sources


Almost every galaxy hosts a BH

99% are silent

1% are active

0.1% have jets


No lobes

Radio lobes

Broad emission lines

No or weak lines emission lines

Weak FRI radio-galaxy

Powerful FRII radio-galaxy


Radio-galaxies & Blazars

FR II poweful radio galaxy, with lobes

FSRQs= Flat Spectrum Radio Quasars, with broad lines

BL Lacs= less powerful, no broad lines

FR I: weak radio galaxy, no lobes

102-103 Rs


Radio VLBI

Optical HST

Superluminal motion


Blazars: phenomenology


Blazars: Spectral Energy Distribution

Radio IR Opt UV X MeV GeV

Inverse Compton

(also possible

hadronic models)

Synchro


The“blazarsequence”

FSRQs

CT

BL Lacs

LBL and HBL

AGILE GLAST

Fossati et al. 1998; Donato et al. 2001


EGRET: ~100 blazars

Cherenkov: ~40 blazars (a few Radiogal)

Gamma-ray blazars

Fermi

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

HESS+ MAGIC


9 years of EGRET (0.1-10 GeV)

Fermi first light, 96 hrs of integration

After 11 months:

~700 (blazars, FSRQsand BL Lacs in equal number)

A few radiogalaxies

4 NLSy1

Starburst galaxies


Blazars: emission models


Coordinated variability at different n

Mkn 421

TeV

PDS

MECS

LECS


BL Lacs: low power, no lines


TeV BL Lacs

Fermi 1 yr 5s

Tagliaferri et al. + MAGIC, 2008


No BLR No IR Torus

Weak cooling Large g

G~ 3

G~50

ADAF? L< 10-3 LEdd?


Emission Models

Simplest scenario: SSC model

No external radiation


Log N(g)

g-n1

gb

Log g

Log nL(n)

ns

n-a1

n-a2

Log n

The simplest model

R

g-n2

B

G

e

q


Log N(g)

Log Usyn(n)

+

gb

n1

n’ s

a1

n2

a2

Log g

Log n

Log nL(n)

ns

nC

a1

a1

a2

a2

Log n

The simplest model


Log N(g)

Log Usyn(n)

gb

n1

n’ s

a1

n2

a2

Log g

Log n

Log nL(n)

nC

ns

a1

aKN

a1

a2

Log n

The simplest model

+

“Klein-Nishina regime”

h n’ s g b >mec2


SSC model: constraining the parameters

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

7 free parameters

Model parameters: R B Nogb n1 n2 d

Observational parameters: ns LsnC LC tvar a1 a2

7 observational quantities

Tavecchio et al. 1998


K

K2


d4

d4

d

d


FSQRs: high power, strong broad emission lines


SX 104 s

Data: Fabian+ 2001


1/2

1/2

RBLR ~ Ldisk

 UBLR= const

RTorus~ Ldisk

 UIR= const

LB ~ B2R2G2c= const  B~1/(RG)

Torus ~1-10 pc

BLR ~0.2 pc


Torus ~1-10 pc

?

?

BLR ~0.2 pc


Importance of g-rays

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

If blob too large (too distant) tvar too long

Then: Rdiss ~ 1000 RS

Energy transport in inner jet must be dissipationless


gb = 103gmax= 104Rdiss= 20Rs G = 10

disk

corona

torus


Log N(g)

n’o

gb

n1

n2

G2

G

Log g

Log nF(n)

ns

nC

a1

a1

a2

a2

Log n

The simplest model - 5

Log nUext(n)

Broad line region,

Disk

+

no

Log n


The simplest model - 6

EC + SSC

3C 279

Ballo et al. 2002

B =0.6 - 0.5d = 17.8- 12.3 gb =550 - 600


A text-book jet

Torus ~8 pc

CMB

  • B propto 1/R

  • n propto 1/R2

  • M=109Mo

  • Ldisk~LEdd

  • z=3

BLR ~0.3 pc


1

SX 105 s

0.1 pc

1


2

1 pc

2


3

10 pc

3


4

100 pc

4


5

1 kpc

5


10 kpc

6

6


100 kpc

7

7


n0

SX 105 s

100 kpc

7

10 kpc

6

1 kpc

5

100 pc

4

10 pc

3

2

1 pc

0.1 pc

1


n0

SX 105 s

100 kpc

7

10 kpc

6

Peak at ~ 100-500 keV

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

Soft X-rays: contributions from larger regions, but within 10 pc (tvar<2.5 months)

1 kpc

5

100 pc

4

10 pc

3

2

1 pc

0.1 pc

1


Fossati et al. 1998; Donato et al. 2001


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

gpeak is the energy of electrons emitting at the peak of the SED

EGRET blazars

Ghisellini et al. 1998


Low power slow cooling large gpeak

Big power fast cooling small gpeak


g-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. 2003

Knot HST-1 (60 pc proj.)

Stawarz et al. 2006

Cheung et al. 2007

Misaligned (20 deg) blazar

Georganopoulos et al. 2005

Lenain et al. 2007

FT and GG 2008

BH horizon

Neronov & Aharonian 2007

Rieger & Aharonian 2008


Core?

Acciari et al. 2008


spine

layer

Ghisellini Tavecchio Chiaberge 2005

Tavecchio & Ghisellini 2008


More seed photons for both

  • Grel= GlayerGspine(1-blayerbspine)

  • 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 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)


Blazar (BL Lac [no BL],FSRQ [BL])

Radiogalaxy (FRI, FRII),

SSRQ

“Unification scheme”

  • Blazar characteristics:

  • - Compact radio core, flat or inverted spectrum

  • - Extreme variability (amplitude and t) at all frequencies

  • High optical and radio polarization

  • FSRQs: bright broad (103-104 km/s) emission lines

  • often evidences for the “blue bump” (acc. disc)

  • BL Lacertae: weak (EW<5 Å) emission lines

  • no signatures of accretion

Urry & Padovani 1995

Narrow Line Region

Broad Line Region

Obscuring torus (hot dust)

Accretion flow/disk (T~1e4 K)

BH


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


e.g. Ferrarese & Ford 2004

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


FRII source: Cygnus A


FRI source: 3C31


VHE emission of M87

t var ~ 2 days !

Light curve

Spectrum


Mkn 501

PKS 2155-304

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

Albert et al. 2007 - MAGIC

New problems: Ultra-rapid variability


Rees 1978 for M87

Observed time: (R0/c)G2(1-bcosq) ~ R0/c !


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


Jet - needle

GG & FT 2008


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 g-rays


threshold

g

x2

q

x1

g

Photon-photon pair production in a nutshell

In astrophysical environments g-rays are effectively absorbed through

g + g -> e+ + e-

Rule of thumb:

In isotropic rad. fields, with declining spectra:


Without any correction:

t (x)= sggR n(1/x) 1/x ~ (1/x)-a ~ xa increasing with E (x=E/mc2)

where n(1/x) 1/x ~ L (1/x) / R2

t (100 GeV)>>1 g-rays cannot escape!!

Internal opacity: limit on d

Observations of gamma rays provide interesting limits on the minimum value of the Doppler factor

Eg=10-100 GeV hn=5-50 eV (UV photons)


Internal opacity: limit on d

e.g. Ghisellini & Dondi 1996

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)

t‘ (x)= t(x)/d4+2a

One can find:

Therefore : d > t (x)1/(4+2a)

Typically d>5


Absorption inside the BLR


Intergalactic absorption


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

Problem and opportunity at the same time!


Extragalactic background light

EBL measurements

Dust

Starlight

Mazin & Raue 2007


3C 273

Mkn 501

M87

Cen A

Coppi & Aharonian 1997

The “g-ray horizon”

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

MediumEBL

MinimumEBL


However, harder intrinsic spectra

can be obtained assuming a power law

electron distribution with a

relatively large lower limit gmin

Synchrotron

Below the corresponding freq.

synchrotron and SSC spectra

are very hard!

Katarzinski et al. 2006

SSC

The absolute limit is:

Fn ~ n1/3


B2

~B (Klein Nishina

B


Jorstad et al. 2001


Superluminal motion


L=L’d4

n=n’ d

Dt=Dt’/d

G

Special relat.

q

1

d =

G (1-b cos q)

Photon “compression”

The relativistic Doppler factor


gb

gb (Klein Nishina)

gb

gb2


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:

?

AGIS, USA

CTA, Europe


Rees 1978 for M87

Observed time: (R0/c)G2(1-bcosq) ~ R0/c !


3C 279 Spada et al. 2001


Mkn 421 Guetta et al. 2004


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