Fabrizio Tavecchio - INAF/OA Brera

Fabrizio TavecchioFabrizio Tavecchio - INAF/OA Brera - INAF/OA Brera

Probing relativistic particles in jets

Standard scenario:

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

N() = No -n n=2 strong, non-relat. shocks; n=2.2 relativistic case

inj >>1 depending upon conditions in the plasma

< max limited by balance acc. rate = cooling rate

Relativistic particles …

Broken-power law distributions expected from continuous injection + cooling

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

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

… in jets

radiogalaxy, RL QSOsblazar

Urr

y &

Padovan

i 1995

Emission lines

EW>5 Å FSRQ

EW<5 Å BL Lac

Synchro

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

Spectral Energy Distribution and emission mechanisms

Inverse Compton(also possiblehadronic models)

Log

Log N()

n1

n2

b

?

?

inj

CoolingCold particlesTotal number: jet power

max

Acceleration

The electron energy distribution

Foss

ati

et

al. 1

99

8;

Don

ato

et

al. 2

00

1

TheThe “blazar“blazar sequence”sequence”FSRQs

BL Lacs

Simbol - X

But see e.g. Padovani 2007

Log

Log N()

n1

n2

b

Low power blazars: probing the high energy end

The simplest model - SSC

Log

Log N()

n1

n2

b +Log

Log Usyn()

1

’ s

Log

Log L()

2

s

2

C

C =’s b2

L()~T c Usyn N() 2 V 4

Tavecchio et al. 2001

Low power blazars: probing the high energy end

Maraschi et al. 1999

Courtesy PO Petrucci

1999

TeV (Whipple)

X-r

ays

X-r

ays

TeV (Whipple)TeV (Whipple)TeV (Whipple)

X-raysX-rays

2000

Maraschi et al. 1999

Fossati et al., in prep

Mkn 421

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.

t(hard/soft)~1000 s

If acc. due to shocks:

B~0.6 10-1 G

Soft

Medium

Hard

Ravasi

o e

t al. 2

004

Mkn 421 XMM-Newton Dec. 2002

TeV spectra and intergalactic absorption

Aharonian et al. 2006 using recent HESS data of the BL Lac 1101-232 (z=0.186) found that, even assuming the lowestlevel of the IR background (estimated through galaxy counts), the de-absorbed spectrum is very hard (<1.5).

The broad-band X-rayspectrum is required toconstrain the intrinsic slope

The broad-band X-rayspectrum is required toconstrain the intrinsic slope

High-Energy Observatories 2004-2020High-Energy Observatories 2004-2020

Log

Log N()

n1

n2

b

High power blazars: probing the low energy end

The simplest model - EC

Log

Log N()

n1

n2

b +Log

Log Uext()

’ o

Log

Log F()

2

s

2

C

Broad line region,Disk

C =’ob2

L()~T c Uext N() 2 V 4

’ o = o

High power blazars: probing the low energy end

Pian et al. 2006

ISGRI 20-40 keV A hard X-ray flare of 3C454.3

Variability …

Luigi Foschini’s talk

Extremely hard slopes…

Tavecchio et al. 2007, in press

Extremely hard! n=1.5!

Suzaku

SWIFT/BAT, 9-month survey

Sambruna et al. 2006

Cold matter: X-ray signatures

Celo

tti, G

his

elli

ni &

Fabia

n 2

00

7

Broad band spectra necessary to obtain effective constraints

Conclusions

The (hard) X-ray band is crucial to address several problemsrelated to the origin and dynamics of relativistic particles in jets

Low energy blazars: probe of the high energy end; particleacceleration; help for the estimate of the CIRB

High power: investigation of low energy electrons; variability; cold particles