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, Ievgen Vovk Andrii Neronov, Ievgen Vovk ISDC Data Centre for Astophysics, Geneva, Switzerland ISDC Data Centre for Astophysics, Geneva, Switzerland
TeV emission from blazars TeV emission from blazars 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) Aharonian et.al. Nature 440:1018-1021, 2006 Aharonian et.al. Nature 440:1018-1021, 2006 In the recent years TeV In the recent years TeV observations of blazars started observations of blazars started to be used for putting to be used for putting constrains on EBL constrains on EBL 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) Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
Secondary -ray emission ɣ ɣ -ray emission from electromagnetic cascade Secondary from electromagnetic cascade TeV TeV Electron-positron Blazar Electron-positron Blazar ɣ ɣ rays rays pairs pairs E e ≈ ≈ E E γ0 / 2 Secondary E e γ0 / 2 Secondary ɣ GeV rays ɣ GeV rays EBL 2 ) 2 E γ = (4/3) ε ε CMB (E e /m e c 2 ) 2 ≈ ≈ E γ = (4/3) CMB (E e /m e c ] 2 2 GeV ≈ 88 [E 88 [E γ0 / 10 TeV] GeV ≈ γ0 / 10 TeV CMB Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
Secondary -ray emission ɣ ɣ -ray emission from electromagnetic cascade Secondary from electromagnetic cascade Electron-positron Electron-positron pairs pairs TeV TeV Blazar Blazar GeV rays ɣ ɣ GeV rays ɣ ɣ rays rays E e ≈ ≈ E E γ0 / 2 E e γ0 / 2 c 2 2 ) ) 2 2 E γ E γ = (4/3) = (4/3) ε ε CMB CMB (E (E e e /m /m e e c ≈ ≈ EBL ≈ 88 [E 88 [E γ0 / 10 TeV] ] 2 2 GeV GeV ≈ γ0 / 10 TeV CMB λ B >> D e : δ ≈ ≈ D D e / R L ≈ ≈ λ B >> D e : δ e / R L -4 [B -16 G -2 ≈ 3x10 3x10 -4 [B / 10 / 10 -16 G] [E ] [E e /10 TeV] -2 ≈ e /10 TeV] λ B << D e : δ ≈ ≈ √( √(D D e λ λ B ) / R R L) ≈ ≈ λ B << D e : δ e B ) / L) -5 [B -16 G -3/2 [ 1/2 ≈ 5x10 5x10 -5 [B / 10 / 10 -16 G] [E ] [E e /10 TeV] -3/2 [λ λ B / 1 kpc] ] 1/2 ≈ e /10 TeV] B / 1 kpc Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
Spectral appearance of electromagnetic cascade Spectral appearance of electromagnetic cascade Courtesy of Andrew Taylor Courtesy of Andrew Taylor Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
Secondary -ray emission ɣ ɣ -ray emission from electromagnetic cascade Secondary from electromagnetic cascade Time delay Time delay Blazar Blazar TeV TeV ɣ ɣ rays rays e + -e - pairs EBL CMB Suppresed Suppresed Extended Extended GeV flux GeV flux emission emission Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
Extragalactic magnetic field (EMF) Extragalactic magnetic field (EMF) Two different broad classes of models Two different broad classes of models of EMF could be identified: of 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 Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
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): -0.8 (95% of signal) Θ ≈ ≈ 2 2˚[E ˚[E γ / 1 GeV] -0.8 (95% of signal) Θ γ / 1 GeV] If PSF at 10 GeV taken as a reference, halo is bigger PSF if B>B PSF : If PSF at 10 GeV taken as a reference, halo is bigger PSF if B>B PSF : -17 τ [E B PSF ≈ 6 x 10 -17 τ [E γ,min / 10 GeV] G, λ λ B > D e B PSF ≈ 6 x 10 γ,min / 10 GeV] G, B > D e -16 τ [E 3/4 [λ -1/2 G, λ B PSF ≈ 8 x 10 -16 τ [E γ,min / 10 GeV] 3/4 [λ B / 1 kpc] -1/2 G, λ B < D e B PSF ≈ 8 x 10 γ,min / 10 GeV] B / 1 kpc] B < D 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. Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
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) Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
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 B for magnetic fields generated at ranges of B, λ B 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) Andrii Neronov, Ievgen Vovk Andrii Neronov, Ievgen Vovk TeVPA 2010, Paris, 21.07.2010 TeVPA 2010, Paris, 21.07.2010 Evidence for strong EMF from Fermi observations of TeV blazars Evidence for strong EMF from Fermi observations of TeV blazars
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