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

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

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 ~ 1029 cm2/s

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)

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)

Hot Spots: shockacceleration

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. 2002

Diffusive Shock Acceleration (Bell 1978; Eichler & Blandford 1987):

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

Heavens & Meisenheimer 1989

Amato & Arons 06 timemp/m±=100

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)

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

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

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

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

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

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

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

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

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

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

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

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