Probing relativistic particles in jets
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Probing relativistic particles in jets. Fabrizio Tavecchio - INAF/OA Brera. Relativistic particles …. Standard scenario: particle acceleration through Fermi I type mechanism at a shock front (“diffusive shock acceleration”):.

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Fabrizio Tavecchio - INAF/OA Brera

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Fabrizio tavecchio inaf oa brera

Probing relativistic particles in jets

Fabrizio Tavecchio - INAF/OA Brera


Fabrizio tavecchio inaf oa brera

Relativistic particles …

Standard scenario:

particle acceleration through Fermi I type mechanism at a shock front (“diffusive shock acceleration”):

N(g) = Nog-n n=2 strong, non-relat. shocks; n=2.2 relativistic case

g > ginj>>1 depending upon conditions in the plasma

g < gmaxlimited by balance acc. rate = cooling rate

n=2 also expected from cooling of high-energy e

Broken-power law distributions expected from continuous injection + cooling

But n2=n1+1 ~3 for blazars we need n2=4-5


Fabrizio tavecchio inaf oa brera

blazar

radiogalaxy, RL QSOs

Urry & Padovani 1995

… in jets

Emission lines

EW>5 Å FSRQ

EW<5 ÅBL Lac


Fabrizio tavecchio inaf oa brera

Spectral Energy Distribution

and emission mechanisms

Radio IR Opt UV X MeV GeV

Inverse Compton

(also possible

hadronic models)

Synchro


Fabrizio tavecchio inaf oa brera

Log N(g)

gb

n1

n2

Log g

The electron energy distribution

ginj

Cooling

Cold particles

Total number: jet power

?

g max

Acceleration

?


Fabrizio tavecchio inaf oa brera

The“blazarsequence”

FSRQs

BL Lacs

Simbol - X

Fossati et al. 1998; Donato et al. 2001

But see e.g. Padovani 2007


Fabrizio tavecchio inaf oa brera

Log N(g)

gb

n1

n2

Log g

Low power blazars: probing the high energy end


Fabrizio tavecchio inaf oa brera

Log N(g)

gb

n1

n2

Log g

nC =n’s gb2 d

Log nL(n)

ns

nC

nL(n)~s T c Usyn N(g)gg2 V d4

a1

a1

a2

a2

Log n

The simplest model - SSC

Log Usyn(n)

+

n’ s

a1

a2

Log n


Fabrizio tavecchio inaf oa brera

Low power blazars: probing the high energy end

Tavecchio et al. 2001

Maraschi et al. 1999

Courtesy PO Petrucci


Fabrizio tavecchio inaf oa brera

1999

Mkn 421

TeV (Whipple)

2000

X-rays

TeV (Whipple)

TeV (Whipple)

Maraschi et al. 1999

X-rays

Fossati et al., in prep


Fabrizio tavecchio inaf oa brera

Mkn 421 XMM-Newton Dec. 2002

Soft

Medium

Hard

Ravasio et al. 2004

Signatures of cooling/acceleration processes are expected.

The best way to detect them is through X-ray monitoring of TeV blazars,

since we can probe the synchrotron emission of the most energetic electrons.

Dt(hard/soft)~1000 s

If acc. due to shocks:

B~0.6 d10-1 G


Fabrizio tavecchio inaf oa brera

TeV spectra and intergalactic absorption


Fabrizio tavecchio inaf oa brera

Aharonian et al. 2006 using recent HESS data of the

BL Lac 1101-232 (z=0.186) found that, even assuming the lowest

level of the IR background (estimated through galaxy

counts), the de-absorbed spectrum is very hard (G<1.5).

The broad-band X-ray

spectrum is required to

constrain the intrinsic

slope


Fabrizio tavecchio inaf oa brera

The broad-band X-ray

spectrum is required to

constrain the intrinsic

slope


Fabrizio tavecchio inaf oa brera

High-Energy Observatories 2004-2020


Fabrizio tavecchio inaf oa brera

Log N(g)

gb

n1

n2

Log g

High power blazars: probing the low energy end


Fabrizio tavecchio inaf oa brera

Log N(g)

gb

n1

n2

Log g

nC =n’ogb2 d

Log nF(n)

ns

nC

nL(n)~s T c Uext N(g)gg2 V d4

a1

a1

a2

a2

Log n

The simplest model - EC

Log Uext(n)

Broad line region,

Disk

+

n’ o

n’ o = G no

Log n


Fabrizio tavecchio inaf oa brera

High power blazars: probing the low energy end


Fabrizio tavecchio inaf oa brera

Variability …

A hard X-ray flare of 3C454.3

ISGRI 20-40 keV

Pian et al. 2006

Luigi Foschini’s talk


Fabrizio tavecchio inaf oa brera

Extremely hard slopes…

Extremely hard! n=1.5!

SWIFT/BAT,

9-month survey

Suzaku

Sambruna et al. 2006

Tavecchio et al. 2007, in press


Fabrizio tavecchio inaf oa brera

Cold matter: X-ray signatures

Celotti, Ghisellini & Fabian 2007

Broad band spectra necessary to obtain effective constraints


Fabrizio tavecchio inaf oa brera

Conclusions

The (hard) X-ray band is crucial to address several problems

related to the origin and dynamics of relativistic particles in

jets

Low energy blazars: probe of the high energy end; particle

acceleration; help for the estimate of the CIRB

High power: investigation of low energy electrons;

variability; cold particles


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