Download - Gianfranco Brunetti
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The interplay of GeV electrons & The interplay of GeV electrons & magnetic fields:magnetic fields: interesting aspects in
galaxies, radio galaxies and clusters
Gianfranco Gianfranco BrunettiBrunettiIstituto di Radioastronomia – INAF, Bologna, ITALY
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OutlineOutline
• Galactic radio halos: BGalactic radio halos: Boo, B, Brmsrms, CRe , CRe diffusiondiffusion
• Physics of CRe acceleration in hot spots Physics of CRe acceleration in hot spots of radiogalaxiesof radiogalaxies
• Origin of CRe in giant radio halos from Origin of CRe in giant radio halos from RM + RM + γγ-rays constraints -rays constraints
• Radio halos in turbulent clusters and Radio halos in turbulent clusters and future LOFAR surveysfuture LOFAR surveys
cluste
rs
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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 ??
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NGC 253(Heesen et al 09)
Convection ??V ~ 300 km/s
Diffusion ??D ~ 1029 cm2/s
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L
Older electrons diffuse on larger scalesand emit at lower frequencies … (??)
Testing diffusion modelsTesting diffusion models
Kol
mog
orov
LL -1/3-1/3 (B/ (B/δδB)B)
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L
Older electrons diffuse on larger scalesand emit at lower frequencies … (??)
Testing diffusion modelsTesting diffusion models
Boh
m
LL BB-1/2-1/2 (B/ (B/δδB)B)
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Hot Spots: shockacceleration
Lobes: evolution(and reacceleration?)
Jets: transport &acceleration
Bow shock
Radio galaxies (hot spots)
(see talk by Saripalli,Orrù ..)
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Electrons (& p) Acceleration :
High energy electrons (emission)
Polarisation and intensity
Heavens & Meisenheimer 1989
Prieto+Brunetti+Mack 2002
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Heavens & Meisenheimer 1989
Meisenheimer 1997; Brunetti +al. 2002
Diffusive Shock Acceleration (Bell 1978; Eichler & Blandford 1987):
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Heavens & Meisenheimer 1989
Meisenheimer 1997; Brunetti +al. 2002
Diffusive Shock Acceleration (Bell 1978; Eichler & Blandford 1987):GHz(~300 MeV)
eLOFAR(50-100 MeV)
B~100-500 μG
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Heavens & Meisenheimer 1989
Amato & Arons 06 timemp/m±=100
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Lazio, Kassim +al. 2006
Measurements of low-energy cut-off ?
This has fundamental implications on the theory of particle acceleration andon the energetics of radio sources: Science Case for Long Baseline LOFAR
See alsoBlundell +al. 2006(6C 0905+3955)
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Clusters of galaxies:largest gravitational structures in the Universe
(M1014-1015Msun RV 2-3 Mpc)
Galaxy cluster mass:
Barions
Dark Matter 80%
5% of stars in galaxies
15-20% of hot diffuse gas
30-300galaxies n10-3cm-3
T107-108K
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van Weeren+al. 2010, Science Vazza, GB, Gheller ,09ShocksShocks
Vazza, GB, et al 2009
TurbulenceTurbulence
Raferty et al 06, Birzan et al. 07
AGN/GWAGN/GWRyu, et al 2003Pfrommer et al 06
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van Weeren+al. 2010, Science Vazza, GB, Gheller ,09ShocksShocks
Vazza, GB, et al 2009
TurbulenceTurbulence
Raferty et al 06, Birzan et al. 07
AGN/GWAGN/GW
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In a fraction of merging clusters: In a fraction of merging clusters:
Radio HalosRadio Halos
Abell 2163Feretti et al. 2001
“Bullet” cluster Govoni et al. 2004
RXCJ 2003-2525 Giacintucci et al. 2007
COMA Brown & Rudnick 2011
1 Mpc
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Hadronic interactionsHadronic 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 ofplasma physics (non-linear interaction between Brms andparticles) and the dissipation of energy in clusters mergers
High energy andneutrino emissionfrom galaxy clusters
The two leading mechanisms
GB & Lazarian 2011
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Gamma raysGamma rays & origin of Radio Halos
< >
Jeltema & Profumo 2011
USSRH
Lγ,π ~ f(δ) <ECR> <Eth/T> Vγ
Lsyn ~ f1(δ) <ECR> <Eth/T> Vsyn B(1+δ/2)(B2+Bcmb2)-1
Coma
Ackermann et al 2010
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Further constraints from FERMI (GB, Blasi, Reimer, Rudnick, Bonafede et al. tbs)
RM
FERMI
UB > 5-10 (UB)RMThis suggests that secondaries due top-p collisions do not play a leading rolein the origin of radio halos
Syn spatial Profile
RH scale 1 Mpc
B(r)=Bo(εTH/ εo)η
0.5
0.2
1.0
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A 521 Coma
A 2256
Heald et al 10Clarke & Ensslin 06
GB et al 08
Brown & Rudnick 11
Gentle CRe acceleration mechanisms : turbulence/Fermi II ?
Τ acc 1-3 108 yrs
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Spectra of radio halos & turbulence Spectra of radio halos & turbulence
0.3 1.4 GHz
moreefficient
lessefficient
Steepening frequency
Χ 1/τacc
Mergers betweenM>1015Msun
Mergers betweenM<1015Msun
Big jumps = major mergersSmall jumps = minor mergers
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Observed spectra of radio halos & turbulence Observed spectra of radio halos & turbulence
0.3 1.4 GHz
lessefficient
Steepening frequency
Χ 1/τacc
Cassano, GB, Setti (2006)
Radio Halos withvery steep spectrumvery steep spectrumin the classical radioband must exist
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Spectral properties of Radio HalosR
ad
io P
ow
er
Frequency
Cassano, GB, Rottgering, Bruggen, 2010 A&A 509 68
more energeticsrare
less energeticscommon
LOFAR is expected to discover 300-400 giant radio halos at z<1.0, a large fraction of them with very steep-spectrum (from less energeticscluster-cluster mergers)
Tier 1Tier 1
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ConclusionsConclusions
• Total intensity & polarization Total intensity & polarization observations provide information on CRe observations provide information on CRe diffusion & Bdiffusion & Brmsrms
• Low frequency observations of radio hot Low frequency observations of radio hot spot constrain the low energy end of the spot constrain the low energy end of the spectrum of the accelerated CRe (injection spectrum of the accelerated CRe (injection problem)problem)
• FERMI FERMI γγ-ray limits give constraint -ray limits give constraint inconsistent with RM in case of hadronic inconsistent with RM in case of hadronic modelsmodels
• LOFAR surveys will allow tests of LOFAR surveys will allow tests of turbulent reacceleration models for giant turbulent reacceleration models for giant radio halosradio halos