Blobs in AGN Jets

IISER Pune

Blobs in AGN Jets

Mayur Shende

IISER Pune

January 20, 2016

Mayur Shende (IISER Pune) Blobs in AGN Jets January 20, 2016 1 / 10

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Introduction

Focus - relativistic jet initiation in blazars

Specifically, episodic jets (as opposed to winds)

To begin with- study data from episodic blobs in the radio galaxy 3C120

Interesting points about 3C 120:

Episodes of radio blob ejection correspond to dips in X-ray luminosity(e.g., Marscher et al 2002, Chatterjee et al 2009)Episodes of radio blob ejection correspond to enhancement in (Fermi)gamma rays (Casadio et al 2015)


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Introduction







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Introduction







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Introduction







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Introduction





Episodes of radio blob ejection correspond to dips in X-ray luminosity(e.g., Marscher et al 2002, Chatterjee et al 2009)

Episodes of radio blob ejection correspond to enhancement in (Fermi)gamma rays (Casadio et al 2015)


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Introduction







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Introduction

Questions:

What are these blobs?

These blobs contain energetic electrons (γ = 105 − 106) confinedwithin a small region

How large are they?

Typical sizes 0.2 − 1.6pc

What are the magnetic fields associated with them (using observationsof synchrotron radiation)?Can these fields confine them (if they are tangled)?


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Introduction

Questions:What are these blobs?


How large are they?




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Introduction



How large are they?




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Introduction



How large are they?




IISER Pune

Introduction



How large are they?




IISER Pune

Introduction



How large are they?


What are the magnetic fields associated with them (using observationsof synchrotron radiation)?

Can these fields confine them (if they are tangled)?


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Introduction



How large are they?




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3C 120: VLBA 15 GHz (Casadio et al 2015)


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3C 120: VLBA 43 GHz (Casadio et al 2015)


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Blob size

Component Size(pc)

C0 0.24C1 0.35E0 0.99E1 1.7E4 1.1E6 1.23E8 0.72E9 0.72D11 0.25D11a 0.19D12 0.11D12a 0.16


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Magnetic Fields and Larmor Radii

Magnetic field (calculated assuming observed (GHz) radiation is atsynchrotron critical frequency)

B =2mcωc

3γ2e

Larmor radius corresponding to this magnetic field

rL =γmc2

eB, = (3/2)

γ3c

ωc

How does this Larmor radius compare with blob size?

i.e., can the magnetic field “confine” the synchrotron emittingelectrons?


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B =2mcωc

3γ2e


rL =γmc2

eB,

= (3/2)γ3c

ωc




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B =2mcωc

3γ2e


rL =γmc2

eB, = (3/2)

γ3c

ωc




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B =2mcωc

3γ2e


rL =γmc2

eB, = (3/2)

γ3c

ωc




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B =2mcωc

3γ2e


rL =γmc2

eB, = (3/2)

γ3c

ωc




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γ = 105 and blob size= 0.24pc

Freq(GHz) B(Gauss) rL(pc) Ratio(rL:blob size)

15 3.57 × 10−7 1.55 × 10−4 6.4 × 10−4

37 8.82 × 10−7 6.27 × 10−5 2.6 × 10−4

43 10.25×10−7 5.4 × 10−5 2.25 × 10−4

γ = 106

Freq(GHz) B(Gauss) rL(pc) Ratio(rL:blob size)

15 3.57 × 10−9 0.1550.65

37 8.82 × 10−9 0.0630.26

43 10.25×10−9 0.0540.23


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Larmor radius to blob size ratio at 15GHz

γ = 105

Blob size(pc) rL(pc) Ratio

0.24 1.55 × 10−4 6.45 × 10−4

0.72 1.55 × 10−4 2.15 × 10−4

1.698 1.55 × 10−4 9.13 × 10−5

γ = 106

Blob size(pc) rL(pc) ratio

0.24 0.1550.65

0.72 0.1550.22

1.698 0.1550.091


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Conclusions

The magnetic fields required to explain the observed GHz emissionrange from 10−7 − 10−9 G assuming γ = 105 − 106

If γ ≈ 105, rL � blob size; i.e., several Larmor radii can fit inside ablob, and the tangled magnetic field can be considered as a goodconfining agent

However, for γ ≈ 106, the Larmor radius is comparable to the blobsize

Hence we need to appeal to additional scattering/confinementmechanisms

Maybe self-generated turbulence?

Thank you for your attention!


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Conclusions








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Conclusions








IISER Pune

Conclusions








IISER Pune

Conclusions








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Conclusions








Blobs in AGN Jets

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