Magnetic Fields in Pulsar Wind Nebulae: an observer s point of view

Transcription

1 Magnetic Fields in Pulsar Wind Nebulae: an observer s point of view Dr. Roland Kothes Dominion Radio Astrophysical Observatory Emergin Technologies National Science Infrastructure National Research Council of Canada Mainz, July 12, 2012 B-fields in PWNe 1 / 31

2 Collaborators Wolfgang Reich (MPIfR) Tom Landecker (DRAO) Samar Safi-Harb (University of Manitoba) Zaven Arzoumanian (Arecibo Observatory) Heather Matheson (University of Manitoba) Konstantin Fedotov (University of Western Ontario) B-fields in PWNe 2 / 31

3 Overview B-fields in PWNe 3 / 31

4 Pulsar Wind Nebulae B-fields in PWNe 4 / 31

5 Pulsar Wind Nebulae B-fields in PWNe 4 / 31

6 Pulsar Wind Nebulae Ω B Ė = E ) (n=1) 0 (1+ t (n 1) τ 0 B tor (r) r 1 B rad (r) r 2 B-fields in PWNe 4 / 31

7 Pulsar Wind Nebulae B-fields in PWNe 4 / 31

8 G Ng et al., 2010 B-fields in PWNe 5 / 31

9 Vela (Helfand et al., 2001) (Dodson et al., 2003) B-field from PA: toroidal RM structure: radial/dipolar (significant internal RM) B-fields in PWNe 6 / 31

10 G : The Boomerang (Kothes et al., 2006) B-field from PA: toroidal RM structure: radial/dipolar (significant internal RM) B-fields in PWNe 7 / 31

11 Crab Nebula (Reich, 2002) B-field from PA: complex RM structure:? (negligible internal RM) (Weisskopf et al., 2000) B-fields in PWNe 8 / 31

12 Crab Nebula (Bietenholz & Kronberg, 1991) B-fields in PWNe 9 / 31

13 3C58 (Slane et al., 2004) (Reich, 2002) B-field from PA: complex, not toroidal RM structure:? (negligible internal RM) B-fields in PWNe 10 / 31

14 G (Safi-Harb et al., 2001) (Fürst et al., 1988; Reich, 2002) B-field from PA: radial RM structure:? B-fields in PWNe 11 / 31

15 G (Kothes et al., 2012, in prep.) B-field from PA: radial RM structure: radial? (significant internal RM) B-fields in PWNe 12 / 31

16 G (Ng et al., 2010) B-field from PA: radial RM structure: radial? (significant internal RM) B-fields in PWNe 13 / 31

17 DA 495 (Kothes et al., 2008) B-field from PA: dipolar RM structure: dipolar (significant internal RM) B-fields in PWNe 14 / 31

18 G Kothes et al., 2012, in prep. B-fields in PWNe 15 / 31

19 PWN Observations: We found toroidal and radial B-field structures Radial B-fields dominate PA and RM Some PWNe show low, some high internal RM Where do the thermal electrons come from? Observations are not consistent with wind scenario predicted by theory: B tor (r) r 1 B rad (r) r 2 B-fields in PWNe 16 / 31

20 Simulations spherical nebula of relativistic particles B-fields in PWNe 17 / 31

21 Simulations spherical nebula of relativistic particles insert magnetic fields of different structure B-fields in PWNe 17 / 31

22 Simulations spherical nebula of relativistic particles insert magnetic fields of different structure simulate the synchrotron emission of this nebula using simple equations: S ν = KB 1 2 (δ+1) ν 1 2 (δ 1),N(E)dE = KE δ de Δφ λ = RMλ 2, RM =0.81 l B n e dl B-fields in PWNe 17 / 31

23 Simulations spherical nebula of relativistic particles insert magnetic fields of different structure simulate the synchrotron emission of this nebula using simple equations: S ν = KB 1 2 (δ+1) ν 1 2 (δ 1),N(E)dE = KE δ de Δφ λ = RMλ 2, RM =0.81 l B n e dl computing observations of this nebula B-fields in PWNe 17 / 31

24 Simulations spherical nebula of relativistic particles insert magnetic fields of different structure simulate the synchrotron emission of this nebula using simple equations: S ν = KB 1 2 (δ+1) ν 1 2 (δ 1),N(E)dE = KE δ de Δφ λ = RMλ 2, RM =0.81 l B n e dl computing observations of this nebula rotation angle Θ: angle between plane of the sky and pulsar spin axis B-fields in PWNe 17 / 31

25 Θ=0 Pure Toroidal Field B-fields in PWNe 18 / 31

26 Θ=30 Pure Toroidal Field B-fields in PWNe 18 / 31

27 Θ=60 Pure Toroidal Field B-fields in PWNe 18 / 31

28 Θ=90 Pure Toroidal Field B-fields in PWNe 18 / 31

29 Toroidal + Radial Field Θ=0 B-fields in PWNe 19 / 31

30 Toroidal + Radial Field Θ=30 B-fields in PWNe 19 / 31

31 Toroidal + Radial Field Θ=60 B-fields in PWNe 19 / 31

32 Toroidal + Radial Field Θ=90 B-fields in PWNe 19 / 31

33 Toroidal + Radial Field Θ=0 B-fields in PWNe 20 / 31

34 Toroidal + Radial Field Θ=30 B-fields in PWNe 20 / 31

35 Toroidal + Radial Field Θ=60 B-fields in PWNe 20 / 31

36 Toroidal + Radial Field Θ=90 B-fields in PWNe 20 / 31

37 Evolution B-fields in PWNe 21 / 31

38 Young PWN: 3C58 Wilson & Weiler, 1976: 1.4 GHz B-fields in PWNe 22 / 31

39 Evolution B-fields in PWNe 23 / 31

40 Evolved PWNe: DA G B-fields in PWNe 24 / 31

41 DA 495 Extrapolating the evolution of DA 495: Let us evolve the flux density and the magnetic field into the future, assuming constant energy. B-fields in PWNe 25 / 31

42 DA 495 Extrapolating the evolution of DA 495: Let us evolve the flux density and the magnetic field into the future, assuming constant energy. If we expand DA 495 it would become invisible when we double its size, in either direction. B-fields in PWNe 25 / 31

43 DA 495 Extrapolating the evolution of DA 495: Let us evolve the flux density and the magnetic field into the future, assuming constant energy. If we expand DA 495 it would become invisible when we double its size, in either direction. This would result in an invisible object that still produces a Faraday rotation of rad/m 2 for polarized emission coming from its background. B-fields in PWNe 25 / 31

44 DA 495 B-fields in PWNe 26 / 31

45 PWNe seem to contain radial and toroidal B-fields, but radial field dominates. The typical magnetic field model for stellar winds is not sufficient to explain the observations. Faraday rotation seems to significantly increase, because the reverse shock pushes the ejecta back into the PWN. Very old PWNe will turn into objects that cannot be seen in emission and may become Faraday lenses. B-fields in PWNe 27 / 31

46 : Simulations B-fields in PWNe 28 / 31

47 : Simulations B-fields in PWNe 29 / 31

48 : 3C58 Wilson & Weiler, 1976: 1.4 GHz B-fields in PWNe 30 / 31

49 : Lenses B-fields in PWNe 31 / 31