Simulating magnetic fields within large scale structure an the propagation of UHECRs

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1 Simulating magnetic fields within large scale structure an the propagation of UHECRs Klaus Dolag ( ) Max-Planck-Institut für Astrophysik ( )

2 Introduction Evolution of the structures in the Universe t = 0.38 Myr Cosmic structure today (T = 13.7 Gyr) Density Temperature Cosmological Simulation CINECA Keyproject Mpc

3 Introduction Evolution of the structures in the Universe t = 0.38 Myr T = 13.7 Gyr "Zoomed" Simulation of a galaxy cluster Density Temperature 275 Mpc Simulation galaxy cluster g1 40 Mpc

4 Observations Cluster wide diffuse synchrotron emission (radio halos) of relativistic electrons in cluster magnetic fields. Origin of relativistic electrons (secondary, shocks, turbulence,...), origin and structure of magnetic fields? 28/10/2008 p.

5 Observations Clarke et al Kim et al Rotation Measure inferred from polarized radio sources as function of distance to the center of galaxy clusters. RM = 812 rad n e B dl m 2 cm 3 µg kpc Clear signature of µg level cluster magnetic fields! 28/10/2008 p.

6 Observations A119 2 Mpc Feretti et al Composite of X-ray map and Rotation Measure in 3 extended radio sources in A119 constrain models for magnetic fields.

7 Observations From Observations: Magnetic field B(r) B 0 ρ gas (r) α Structure describe by magnetic power spectra with index n Rotation Measure alone leads to n -3. Radio halo and polarization needs varying from -2 to -4 when going from center to periphery. Structure complex, degeneration of parameters. Open questions: Signature of cluster dynamics? Signature of turbulence/decay of magnetic field? Do cosmological MHD simulations!

8 Cosmological MHD Simulations Origin Primordial Battery Dynamo (Turbulence) Stars Supernova Galactic Winds AGN, Jets Rees 1994 Shocks + further amplification by structure formation! - dissipation?

9 Cosmological MHD Simulations Induction equation ( B( v) + ( B ) v): d B i dt = fco i Ha 2 ρ i N j=1 [ m Bi j ( v ij i Wij ) v ij ( B i ] i Wij ) 2B i ( 1 = dt ) and magnetic Lorenz force Ha 2 da d v i dt = a3γ 1 µ 0 N j=1 M kl i = [ m j fi co M i ρ 2 i i Wi + f co j ( B ki B li 12 B i 2 δ kl ) M j ρ 2 j j Wj ] with a 3γ = dt dη. Instable in magnetic field dominated situations!!

10 Cosmological MHD Simulations Code verification in 1D shock tube tests (Ryu & Johns 1995)... Code verification various 2D tests... Magnetic field in the vortex (Orszag & Tang 1979) and the rotor ( Balsare & Spicer 1999) test problem. Results for Anthena (top left) and SPH-MHD runs Dolag & Stasyszyn 2008.

11 Cosmological MHD Simulations Application to galaxy cluster formation Mpc 68.4 Mpc DEC Observation Simulation 684 kpc 6.84 Mpc 3C449 Feretti et al RA RM (counts) (RAD/M/M) Zoomed Galaxy Cluster simulations, (Dolag & Stasyszyn 2008). 28/10/2008 p.

12 Cosmological MHD Simulations Saturation Shear + Turbulence + Major Merger Shear Predicting magnetic field amplification (Dolag et al. 2004/2005). Analysis of structure/evolution by R. Pakmor (Diplom, MPA).

13 Cosmological MHD Simulations R. Pakmor (Diplomarbeit) Magnetic field power spectra within large cluster volume not a simple power law. Physics or resolution (adaptive)? Compare with observations. 28/10/2008 p.

14 Cosmological MHD Simulations rad/m Independent of initial field configuration Dolag et al B(r) ρ(r), curved magnetic power spectrum 28/10/2008 p.

15 The Local Universe Magnetic Field structure in Local Universe? Charged particle astronomy possible? Hudson /10/2008 p.

16 The Local Universe Saunders et al IRAS Galaxies

17 The Local Universe Run movie Mathis et al 2002 (DM-Only), Dolag et al 2004 (Gas + MHD)

18 The Local Universe Seeding magnetic fields as galactic outflows (Donnert et al. 2008). 28/10/2008 p.

19 The Local Universe Testing influence of different wind parameters (Donnert et al. 2008). 28/10/2008 p.

20 The Local Universe Donnert & Dolag 2008 B ~ rho^0.5 B ~ rho Different scenarios Bonafede et al Predicted by numerical simulations: B(r) n(r) Frozen in magnetic field: B(r) n(r) 2/3 Equipatition magnetic field: B(r) n(r) 1/2 compatible with still rare observations. 28/10/2008 p.

21 The Local Universe Region shown is (50 Mpc) 3 centered between Centaurus and Pavo. Filaments and bridges between clusters, but be careful: Never straight lines! Always junctions of sheets! Sometimes projections of sheets!

22 The Local Universe Size of clusters Region of alignment Going along a filament 28/10/2008 p.

23 The Local Universe "best" B run "high" B run Slice perpendicular to a filament 28/10/2008 p.

24 Propagation of UHECRs Trajectories of cosmic Rays diffusing through the cluster core. Rordorf et al /10/2008 p.

25 Propagation of UHECRs Centaurus Milky Way Full sky deflection signal for ev Cosmic Rays for two different observer position, using a sphere with radius 35Mpc.

26 Propagation of UHECRs no losses with losses Full sky deflection signal for ev Cosmic Rays with and without losses by photo-pion production in collisions with CMB, using a sphere of 100Mpc radius. 28/10/2008 p.

27 Propagation of UHECRs Virgo Coma Centaurus Hydra A3627 Perseus Pavo Full sky deflection signal for ev Cosmic Rays without losses, using a sphere of 110Mpc radius.

28 Dolag, Kachelriess, Semikoz /10/2008 p. Propagation of UHECRs Sky maps of UHECRs emitted uniformly from M87 with 1000 (upper right), 100, 10 and 1EeV (lower left).

29 Conclusions B 0 (0.2 1) (1 + z) 2 Gauss injected at z > 3 results in reasonable cluster magnetic fields. Simulation predicts scalings and relations which can be observational tested.! Almost independent of details of seed creation mechanism.! Homogenous initial seed results to upper limit in deflections by low density regions. Diffusion of UHECRs in cluster cores can lead to anisotropic emission. Deflections are small enough to allow pointing of sources of UHECRs with energies ev over most of the sky.

Magnetic Fields in Evolving Spiral Galaxies and their Observation with the SKA

Magnetic Fields in Evolving Spiral Galaxies and their Observation with the SKA Rainer Beck MPIfR Bonn & SKA Science Working Group Fundamental magnetic questions When and how were the first fields generated?