The interplay of GeV electrons & The interplay of GeV electrons & magnetic fields: magnetic fields: interesting aspects in galaxies, radio galaxies and clusters Gianfranco Gianfranco Brunetti Brunetti Istituto di Radioastronomia – INAF, Bologna, ITALY
The interplay of GeV electrons & magnetic fields: interesting aspects in galaxies, radio galaxies and clusters. Gianfranco Brunetti. Istituto di Radioastronomia – INAF, Bologna, ITALY. Outline Galactic radio halos: B o , B rms , CRe diffusion - PowerPoint PPT Presentation
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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
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 … (??)
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