The interplay of GeV electrons & magnetic fields: The interplay of GeV electrons & magnetic fields: interesting aspects in galaxies, radio galaxies and clusters Gianfranco Brunetti Istituto di Radioastronomia – INAF, Bologna, ITALY

Outline Outline Galactic radio halos: B o, B rms, CRe diffusion Galactic radio halos: B o, B rms, CRe diffusion Physics of CRe acceleration in hot spots of radiogalaxies Physics of CRe acceleration in hot spots of radiogalaxies Origin of CRe in giant radio halos from RM + γ -rays constraints Origin of CRe in giant radio halos from RM + γ -rays constraints Radio halos in turbulent clusters and future LOFAR surveys Radio halos in turbulent clusters and future LOFAR surveys clusters

Galactic radio halos (see talk by Chyzy..) NGC 253 (Heesen et al 09) NGC 4631 (Krause 09) Diffusion and transport of CRe perpendicular to the galactic plane.. - How extended ?? - Structure & strength of B on LS ?? - Winds/convection or diffusion ??

NGC 253 (Heesen et al 09) Convection ?? V ~ 300 km/s Diffusion ?? D ~ cm 2 /s

L Older electrons diffuse on larger scales and emit at lower frequencies … (??) Testing diffusion models Kolmogorov L -1/3 (B/δB) -1/3 (B/δB)

L Older electrons diffuse on larger scales and emit at lower frequencies … (??) Testing diffusion models Bohm L B -1/2 (B/δB) B -1/2 (B/δB)

Hot Spots: shock acceleration Lobes: evolution (and reacceleration?) Jets: transport & acceleration Bow shock Radio galaxies (hot spots) (see talk by Saripalli, Orrù..)

Electrons (& p) Acceleration : High energy electrons (emission) Polarisation and intensity Heavens & Meisenheimer 1989 Prieto+Brunetti+Mack 2002

Heavens & Meisenheimer 1989 Meisenheimer 1997; Brunetti +al Diffusive Shock Acceleration (Bell 1978; Eichler & Blandford 1987):

Heavens & Meisenheimer 1989 Meisenheimer 1997; Brunetti +al Diffusive Shock Acceleration (Bell 1978; Eichler & Blandford 1987): GHz (~300 MeV) eLOFAR ( MeV) B~ μG

Heavens & Meisenheimer 1989 Amato & Arons 06 time m p /m ± =100

Lazio, Kassim +al Measurements of low-energy cut-off ? This has fundamental implications on the theory of particle acceleration and on the energetics of radio sources: Science Case for Long Baseline LOFAR See also Blundell +al (6C )

Clusters of galaxies: largest gravitational structures in the Universe (M  M sun R V  2-3 Mpc) Galaxy cluster mass: Barions Dark Matter 80% 5% of stars in galaxies 15-20% of hot diffuse gas  galaxies n  cm -3 T  K

van Weeren+al. 2010, Science Vazza, GB, Gheller,09 Shocks Vazza, GB, et al 2009 Turbulence Raferty et al 06, Birzan et al. 07 AGN/GW Ryu, et al 2003 Pfrommer et al 06

van Weeren+al. 2010, Science Vazza, GB, Gheller,09 Shocks Vazza, GB, et al 2009 Turbulence Raferty et al 06, Birzan et al. 07 AGN/GW

In a fraction of merging clusters: Radio Halos Abell 2163 Feretti et al “Bullet” cluster Govoni et al RXCJ Giacintucci et al COMA Brown & Rudnick Mpc

Hadronic interactions (Dennison 1980, Blasi & Colafrancesco 99,..) Turbulence and stochastic (re)acceleration (Brunetti et al 01, Petrosian 01, many others..) FERMI Miniati 2003 Radio halos probe effects of plasma physics (non-linear interaction between Brms and particles) and the dissipation of energy in clusters mergers High energy and neutrino emission from galaxy clusters The two leading mechanisms GB & Lazarian 2011

Gamma rays Gamma rays & origin of Radio Halos <> Jeltema & Profumo 2011 USSRH L γ,π ~ f(δ) V γ L syn ~ f 1 (δ) V syn B (1+ δ/2) (B 2 +B cmb 2 ) -1 Coma Ackermann et al 2010

Further constraints from FERMI (GB, Blasi, Reimer, Rudnick, Bonafede et al. tbs) RM FERMI U B > 5-10 (U B ) RM This suggests that secondaries due to p-p collisions do not play a leading role in the origin of radio halos Syn spatial Profile RH scale  1 Mpc B(r)=B o ( ε TH / ε o ) η

A 521 Coma A 2256 Heald et al 10 Clarke & Ensslin 06 GB et al 08 Brown & Rudnick 11 Gentle CRe acceleration mechanisms : turbulence/Fermi II ? Τ acc  yrs

Spectra of radio halos & turbulence GHz more efficient less efficient Steepening frequency Χ  1/τ acc Mergers between M>10 15 M sun Mergers between M<10 15 M sun Big jumps = major mergers Small jumps = minor mergers

Observed spectra of radio halos & turbulence GHz less efficient Steepening frequency Χ  1/τ acc Cassano, GB, Setti (2006) Radio Halos with very steep spectrum in the classical radio band must exist

Spectral properties of Radio Halos Radio Power Frequency Cassano, GB, Rottgering, Bruggen, 2010 A&A more energetics rare less energetics common LOFAR is expected to discover giant radio halos at z<1.0, a large fraction of them with very steep-spectrum (from less energetics cluster-cluster mergers) Tier 1

Conclusions Conclusions Total intensity & polarization observations provide information on CRe diffusion & B rms Total intensity & polarization observations provide information on CRe diffusion & B rms Low frequency observations of radio hot spot constrain the low energy end of the spectrum of the accelerated CRe (injection problem) Low frequency observations of radio hot spot constrain the low energy end of the spectrum of the accelerated CRe (injection problem) FERMI γ -ray limits give constraint inconsistent with RM in case of hadronic models FERMI γ -ray limits give constraint inconsistent with RM in case of hadronic models LOFAR surveys will allow tests of turbulent reacceleration models for giant radio halos LOFAR surveys will allow tests of turbulent reacceleration models for giant radio halos