Evidence for strong Extragalactic Magnetic Fields Evidence for - - PowerPoint PPT Presentation

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Evidence for strong Extragalactic Magnetic Fields Evidence for strong Extragalactic Magnetic Fields from Fermi observations of TeV blazars from Fermi observations of TeV blazars

Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk

ISDC Data Centre for Astophysics, Geneva, Switzerland ISDC Data Centre for Astophysics, Geneva, Switzerland

SLIDE 2

Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

TeV emission from blazars TeV emission from blazars

Aharonian et.al. Nature 440:1018-1021, 2006 Aharonian et.al. Nature 440:1018-1021, 2006 SED of H 2356−309. Aharonian et.al., SED of H 2356−309. Aharonian et.al., A&A 455, 461-466 (2006) A&A 455, 461-466 (2006)

TeV emission from distant TeV emission from distant blazars is absorbed on the blazars is absorbed on the Extragalactic Background Light Extragalactic Background Light (EBL) (EBL) In the recent years TeV In the recent years TeV

• bservations of blazars started
• bservations of blazars started

to be used for putting to be used for putting constrains on EBL constrains on EBL

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Secondary Secondary -ray emission ɣ-ray emission ɣ from electromagnetic cascade from electromagnetic cascade

E Eγ

γ = (4/3)

= (4/3) ε εCMB

CMB (E

(Ee

e/m

/me

ec

c2

2)

)2

2

≈ ≈ ≈ ≈ 88 [E 88 [Eγ0

γ0 / 10 TeV

/ 10 TeV] ]2

2 GeV

GeV E Ee

e

≈ ≈ E Eγ0

γ0 / 2

/ 2 Blazar Blazar EBL CMB TeV TeV rays ɣ rays ɣ Secondary Secondary GeV rays ɣ GeV rays ɣ Electron-positron Electron-positron pairs pairs

SLIDE 4

Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Secondary Secondary -ray emission ɣ-ray emission ɣ from electromagnetic cascade from electromagnetic cascade

E Eγ

γ = (4/3)

= (4/3) ε εCMB

CMB (E

(Ee

e/m

/me

ec

c2

2)

)2

2

≈ ≈ ≈ ≈ 88 [E 88 [Eγ0

γ0 / 10 TeV

/ 10 TeV] ]2

2 GeV

GeV E Ee

e

≈ ≈ E Eγ0

γ0 / 2

/ 2 Blazar Blazar EBL CMB TeV TeV rays ɣ rays ɣ GeV rays ɣ GeV rays ɣ Electron-positron Electron-positron pairs pairs λ λB

B >> D

>> De

e : δ

: δ ≈ ≈ D De

e / R

/ RL

L

≈ ≈ ≈ ≈ 3x10 3x10-4

• 4 [B

[B / 10 / 10-16

• 16 G

G] [E ] [Ee

e/10 TeV]

/10 TeV]-2

• 2

λ λB

B << D

<< De

e : δ

: δ ≈ ≈ √( √(D De

e

λ λB

B) /

) / R RL)

L)

≈ ≈ ≈ ≈ 5x10 5x10-5

• 5 [B

[B / 10 / 10-16

• 16 G

G] [E ] [Ee

e/10 TeV]

/10 TeV]-3/2

• 3/2 [

[λ λB

B / 1 kpc

/ 1 kpc] ]1/2

1/2

SLIDE 5

Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Spectral appearance of electromagnetic cascade Spectral appearance of electromagnetic cascade

Courtesy of Andrew Taylor Courtesy of Andrew Taylor

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Secondary Secondary -ray emission ɣ-ray emission ɣ from electromagnetic cascade from electromagnetic cascade

Blazar Blazar EBL CMB TeV TeV rays ɣ rays ɣ e+-e- pairs

Time delay Time delay Extended Extended emission emission Suppresed Suppresed GeV flux GeV flux

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Extragalactic magnetic field (EMF) Extragalactic magnetic field (EMF)

Two different broad classes of models Two different broad classes of models

• f EMF could be identified:
• f EMF could be identified:

“ “Astrophysical” models Astrophysical” models: EMF were : EMF were formed at the epoch of galaxy formed at the epoch of galaxy

• formation. Resulting EMF should be
• formation. Resulting EMF should be

strong near galaxies, but very weak in strong near galaxies, but very weak in the space far away from galaxies the space far away from galaxies “ “Cosmological” models Cosmological” models: EMF were : EMF were formed prior to formation of galaxies. formed prior to formation of galaxies. Resulting field should fill the whole Resulting field should fill the whole Universe Universe

SLIDE 8

Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Looking for the suppression of GeV flux Looking for the suppression of GeV flux

Fermi/LAT satellite observes in GeV band. Fermi/LAT satellite observes in GeV band. Public data are available since August 2008. Public data are available since August 2008. Lower energy electrons are deviated by larger angles. Lower energy electrons are deviated by larger angles. The size of extended cascade source is larger at lower energies. The size of extended cascade source is larger at lower energies. Fermi/LAT point spread function (PSF): Fermi/LAT point spread function (PSF): Θ Θ ≈ ≈ 2 2˚[E ˚[Eγ

γ / 1 GeV]

/ 1 GeV]-0.8

• 0.8 (95% of signal)

(95% of signal) If PSF at 10 GeV taken as a reference, halo is bigger PSF if B>B If PSF at 10 GeV taken as a reference, halo is bigger PSF if B>BPSF

PSF:

: B BPSF

PSF ≈ 6 x 10

≈ 6 x 10-17

• 17 τ [E

τ [Eγ,min

γ,min / 10 GeV] G,

/ 10 GeV] G, λ λB

B > D

> De

e

B BPSF

PSF ≈ 8 x 10

≈ 8 x 10-16

• 16 τ [E

τ [Eγ,min

γ,min / 10 GeV]

/ 10 GeV]3/4

3/4 [λ

[λB

B / 1 kpc]

/ 1 kpc]-1/2

• 1/2 G, λ

G, λB

B < D

< De

e

In this case we start to loose the flux from point-like blazar. In this case we start to loose the flux from point-like blazar. A way to look for EMF. A way to look for EMF.

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Observed suppression of GeV flux Observed suppression of GeV flux

4 TeV blazars were selected for the 4 TeV blazars were selected for the analysis based on their high redshifts analysis based on their high redshifts and hard TeV band spectra: and hard TeV band spectra: 1ES 0229+200 (z = 0.14), 1ES 0229+200 (z = 0.14), H 2356-309 (z = 0.165), H 2356-309 (z = 0.165), 1ES 1101-232 (z = 0.186), 1ES 1101-232 (z = 0.186), 1ES 0347-121 (z = 0.188). 1ES 0347-121 (z = 0.188). None of them was detected with None of them was detected with Fermi/LAT. Fermi/LAT. Upper limits of their flux in GeV band Upper limits of their flux in GeV band put constrains on the possible put constrains on the possible cascade contribution and, thus, on cascade contribution and, thus, on the parameters of EMF. the parameters of EMF.

• A. Neronov and Ie. Vovk,
• A. Neronov and Ie. Vovk,

Science 328, 73 (2010) Science 328, 73 (2010)

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Derived constrains on EMF Derived constrains on EMF

The black hatched region shows the lower The black hatched region shows the lower bound on the EGMF derived in this work. bound on the EGMF derived in this work. Orange hatched regions show the allowed

Orange hatched regions show the allowed ranges of B, λ ranges of B, λB

B for magnetic fields generated at

for magnetic fields generated at the epoch of: the epoch of: Inflation Inflation (horizontal hatching) (horizontal hatching) the electroweak phase transition the electroweak phase transition (dense vertical hatching), (dense vertical hatching), QCD phase transition QCD phase transition (medium vertical hatching), (medium vertical hatching), epoch of recombination epoch of recombination (rear vertical hatching) (rear vertical hatching)

• A. Neronov and Ie. Vovk,
• A. Neronov and Ie. Vovk,

Science 328, 73 (2010) Science 328, 73 (2010)

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Summary Summary

Observed absence of predicted cascade emission provides Observed absence of predicted cascade emission provides the first evidence for the existence of strong magnetic field the first evidence for the existence of strong magnetic field in the voids of the Large-Scale Structure. in the voids of the Large-Scale Structure. The reported here lower bound is The reported here lower bound is (for correlation lengths above ~ 1 MPc) (for correlation lengths above ~ 1 MPc) B ~ 3x10 B ~ 3x10-16

• 16 G

G Evidence for the existence of magnetic fields in voids provides a Evidence for the existence of magnetic fields in voids provides a strong argument in favor of cosmological origin of “seed” strong argument in favor of cosmological origin of “seed” magnetic field. magnetic field. The lower bound reported here excludes substantial parts of The lower bound reported here excludes substantial parts of allowed parameter space for all the classes of cosmological allowed parameter space for all the classes of cosmological magnetogenesis models. magnetogenesis models.

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Thank you for your attention! Thank you for your attention!

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Appearance of extended emission Appearance of extended emission

Neronov et. al., Neronov et. al., arXiv:1002.4981v1 arXiv:1002.4981v1

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Discovery of gamma-ray halos around AGNs Discovery of gamma-ray halos around AGNs

• Sh. Ando, A. Kusenko, arXiv:1005.1924
• Sh. Ando, A. Kusenko, arXiv:1005.1924

There are halos, thus there should be There are halos, thus there should be magnetic field... magnetic field...

Is Is anything anything missing missing? ?

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Andrii Neronov, Andrii Neronov, Ievgen Vovk Ievgen Vovk Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars

TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010

Discovery of gamma-ray halos around AGNs Discovery of gamma-ray halos around AGNs ? ?

Neronov et.al., arXiv:1006.0164 Neronov et.al., arXiv:1006.0164

There are no halos observed. There are no halos observed. Difference between approximation Difference between approximation and real PSF found. and real PSF found.