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.

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Flat Radio Sources

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Flat radio sources

Flat Radio Sources


Flat radio sources

Almost every galaxy hosts a BH

99% are silent

1% are active

0.1% have jets


Flat radio sources

No lobes

Radio lobes

Broad emission lines

No or weak lines emission lines

Weak FRI radio-galaxy

Powerful FRII radio-galaxy


Radio galaxies blazars

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


Flat radio sources

Radio VLBI

Optical HST

Superluminal motion


Flat radio sources

Blazars: phenomenology


Flat radio sources

Blazars: Spectral Energy Distribution

Radio IR Opt UV X MeV GeV

Inverse Compton

(also possible

hadronic models)

Synchro


Flat radio sources

The“blazarsequence”

FSRQs

CT

BL Lacs

LBL and HBL

AGILE GLAST

Fossati et al. 1998; Donato et al. 2001


Gamma ray blazars

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


Flat radio sources

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


Flat radio sources

Blazars: emission models


Flat radio sources

Coordinated variability at different n

Mkn 421

TeV

PDS

MECS

LECS


Flat radio sources

BL Lacs: low power, no lines


Flat radio sources

TeV BL Lacs

Fermi 1 yr 5s

Tagliaferri et al. + MAGIC, 2008


Flat radio sources

No BLR No IR Torus

Weak cooling Large g

G~ 3

G~50

ADAF? L< 10-3 LEdd?


Flat radio sources

Emission Models

Simplest scenario: SSC model

No external radiation


Flat radio sources

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


Flat radio sources

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


Flat radio sources

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


Flat radio sources

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


Flat radio sources

K

K2


Flat radio sources

d4

d4

d

d


Flat radio sources

FSQRs: high power, strong broad emission lines


Flat radio sources

SX 104 s

Data: Fabian+ 2001


Flat radio sources

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


Flat radio sources

Torus ~1-10 pc

?

?

BLR ~0.2 pc


Flat radio sources

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


Flat radio sources

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

disk

corona

torus


Flat radio sources

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


Flat radio sources

The simplest model - 6

EC + SSC

3C 279

Ballo et al. 2002

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


Flat radio sources

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


Flat radio sources

1

SX 105 s

0.1 pc

1


Flat radio sources

2

1 pc

2


Flat radio sources

3

10 pc

3


Flat radio sources

4

100 pc

4


Flat radio sources

5

1 kpc

5


Flat radio sources

10 kpc

6

6


Flat radio sources

100 kpc

7

7


Flat radio sources

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


Flat radio sources

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


Flat radio sources

Fossati et al. 1998; Donato et al. 2001


Flat radio sources

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


Flat radio sources

Low power slow cooling large gpeak

Big power fast cooling small gpeak


Flat radio sources

g-ray emission from non-blazar AGNs

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

the radiogalaxy M87


Flat radio sources

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


Flat radio sources

Core?

Acciari et al. 2008


Flat radio sources

spine

layer

Ghisellini Tavecchio Chiaberge 2005

Tavecchio & Ghisellini 2008


More seed photons for both

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


Flat radio sources

BL Lac

Radiogalaxy


Flat radio sources

Misaligned structured blazar jet

FT and GG 2008


Flat radio sources

The End


Flat radio sources

Evidences for relativistic beaming

Superluminal motions

Level of Compton emission

High brightness temperatures

Gamma-ray emission/absorption (see below)


Flat radio sources

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


Flat radio sources

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


Flat radio sources

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


Flat radio sources

FRII source: Cygnus A


Flat radio sources

FRI source: 3C31


Flat radio sources

VHE emission of M87

t var ~ 2 days !

Light curve

Spectrum


Flat radio sources

Mkn 501

PKS 2155-304

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

Albert et al. 2007 - MAGIC

New problems: Ultra-rapid variability


Flat radio sources

Rees 1978 for M87

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


Flat radio sources

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)


Flat radio sources

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


Flat radio sources

Jet - needle

GG & FT 2008


Flat radio sources

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


Flat radio sources

Absorption of g-rays


Flat radio sources

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:


Flat radio sources

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)


Flat radio sources

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


Flat radio sources

Absorption inside the BLR


Flat radio sources

Intergalactic absorption


Flat radio sources

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!


Flat radio sources

Extragalactic background light

EBL measurements

Dust

Starlight

Mazin & Raue 2007


Flat radio sources

3C 273

Mkn 501

M87

Cen A

Coppi & Aharonian 1997

The “g-ray horizon”

Mean free path


Flat radio sources

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


Flat radio sources

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


Flat radio sources

B2

~B (Klein Nishina

B


Flat radio sources

Jorstad et al. 2001


Flat radio sources

Superluminal motion


Flat radio sources

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


Flat radio sources

gb

gb (Klein Nishina)

gb

gb2


Flat radio sources

Absorption inside the BLR - 2


Flat radio sources

Constraints from 3C279

Albert at al. 2008


Flat radio sources

VHE emission of FSRQs

3C 279, z=0.536

Albert at al. 2008


Flat radio sources

The future -2

New Cherenkov Telescope Arrays:

?

AGIS, USA

CTA, Europe


Flat radio sources

Rees 1978 for M87

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


Flat radio sources

3C 279 Spada et al. 2001


Flat radio sources

Mkn 421 Guetta et al. 2004


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