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Fabrizio Tavecchio
INAF-Oss. Astron. di Brera, Italy
Blazars and cosmic bkgs. Fabrizio Tavecchio INAF-Oss. Astron. di - - PowerPoint PPT Presentation
Blazars and cosmic bkgs. Fabrizio Tavecchio INAF-Oss. Astron. di - - PowerPoint PPT Presentation
Blazars and cosmic bkgs. Fabrizio Tavecchio INAF-Oss. Astron. di Brera, Italy Introduction: AGNs, blazars Blazars: phenomenology Blazars: emission models Absorption of gamma-rays: backgrounds and the intergalactic B-field INTRODUCTION
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INTRODUCTION
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Almost all galaxies contain a massive black hole
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Almost all galaxies contain a massive black hole
e.g. Ferrarese & Ford 2004
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Almost all galaxies contain a massive black hole 99% of them is (almost) silent (e.g. our Galaxy)
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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 radio
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Powerful (FRII) Radiogalaxy: Cygnus A
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Weak (FRI) radiogalaxy: 3C31
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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
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BH Broad Line Region Narrow Line Region
Urry & Padovani 1995
“Unification scheme”
Accretion flow/disk (T~1e4 K)
Obscuring torus (hot dust)
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Radiogalaxy (FRI, FRII), SSRQ
BH Broad Line Region Narrow Line Region
Urry & Padovani 1995
“Unification scheme”
Accretion flow/disk (T~1e4 K)
Obscuring torus (hot dust)
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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)
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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 (1000-10000 km/s) emission lines
- ften evidences for the “blue bump” (acc. disc)
BL Lacertae: weak (EW<5 Å) emission lines no signatures of accretion
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Evidences for relativistic beaming
Superluminal motions Level of Compton emission High brightness temperatures Gamma-ray emission/absorption
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Radio VLBI Optical HST
Superluminal motion
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Superluminal motion
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Jorstad et al. 2001
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Blazars: phenomenology
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The Fermi/LAT (0.1-100 GeV) sky
2LAC: (2 years) 395 BL Lac 310 FSRQ 5 radiogalaxy 2 SSRQ
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The VHE extragalactic gamma-ray sky
38 BL Lacertae 5 radiogalaxies 3 FSRQ (3C279, z=0.536)
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The bumpy spectral energy distribution
Bonnoli et al. 2010
The brightest source in GeV!
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LAT lightcurve
FT et al. 2010 See also Foschini et al. 2010 Abdo et al. 2010, arXiv:1007
.0483 for 3C454.3
The erratic light-curve
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Rapid variability implies compact regions!
Conical geometry
IF
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Fossati et al. 1998; Donato et al. 2001
FSRQs
BL Lacs
The “blazar sequence”
Blazars
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Fossati et al. 1998; Donato et al. 2001
FSRQs CT
AGILE Fermi
The “blazar sequence”
BL Lacs
Swift
Blazars
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Blazars: emission models
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BL Lacs: “clean” jets
Inefficient accretion flow (ADAF-ADIOS)*
*but see Raiteri et al. 2009 Capetti et al. 2010 for BL Lac itself
Blazars
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Emission Models
Simplest scenario: SSC model (HBL) Other : external radiation (LBL, FSRQs, HBL?)
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The relativistic Doppler factor
- =
1
(1 cos )
Special relat. Photon “compression”
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The relativistic Doppler factor
- L=L’4
=’ t=t’/
=
1
(1 cos )
Special relat. Photon “compression”
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The relativistic Doppler factor
- L=L’4
=’ t=t’/
=
1
(1 cos )
Special relat. Photon “compression”
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Coordinated variability at different
Mkn 421
X-rays TeV
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One-zone Synch. Self-Compton models
Tagliaferri et al. + MAGIC Coll. 2008
- B
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One-zone Synch. Self-Compton models
Tagliaferri et al. + MAGIC Coll. 2008
- B
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The simplest model - 1
- R
Log Log N() n1 n2 b Log Log L() 1 2 s B e
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The simplest model – 2a
Log Log N() n1 n2 b Log Usyn()
+
Log 1 2 ’s Log Log L() 1 2 s 1 2 C
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The simplest model – 2b
Log Log N() n1 n2 b
+
“Klein-Nishina regime” h ’s b >mec2 Log L() Log 1 2 s 1 KN C Log Log Usyn() 1 2 ’s
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Mkn 421: a BL Lac
"Pure" SSC
The simplest model - 4
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In principle, in the simplest version of the SSC model, all the parameters can be constrained by quantities available from
- bservations:
Model parameters: R B No b n1 n2 Observational parameters: s Ls C LC tvar 1 2
7 free parameters 7 observational quantities
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FSRQs: the general scenario
Accretion disk
Blazars
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FSRQs: the general scenario
X-ray corona
Blazars
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FSRQs: the general scenario
BLR
Blazars
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DUSTY TORUS
FSRQs: the general scenario
Blazars
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e-
- e-
e-
- B
FSRQs: the “canonical” scenario
Dermer et al. 2009 Ghisellini, FT 2009 Sikora et al. 2009 Accretion disk X-ray corona BLR
DUSTY TORUS Blazars
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The simplest model - 5
Log Log N() n1 n2 b
+
Log Log Uext()
Broad line region,
Disk
- ’o
- 2
Log Log F() 1 2 s 1 2 C
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B = 0.6 - 0.5 = 17.8 - 12.3 b = 550 - 600