Magnetic fields in and beyond clusters of galaxiesweb.phys.ntnu.no/~mika/dolag.pdf · Magnetic...
Transcript of Magnetic fields in and beyond clusters of galaxiesweb.phys.ntnu.no/~mika/dolag.pdf · Magnetic...
Magnetic fields in and beyondclusters of galaxies
Klaus Dolag
Perseus
Hydra
Coma
A3627
Virgo
Pavo
Centaurus
Donnert, Dolag et al. 2009
17/06/2009 – p. 1
IntroductionCMB
Cosmic structure today
TemperatureDensity
275 Mpc
(t = 0.38 Myr)
(t = 13.7 Gyr)
Borgani, Murante, Springel, Diaferio, Dolag et al. 2004
The cosmic web today (z = 0) is mainly accessible throughsimulations (warm, thin). Model predictions for~B are importantfor propagation of ultra high energetic cosmic rays (UHECRs).
17/06/2009 – p. 2
Introduction
Temperature
275 Mpc
40 Mpc
Density
"Zoomed" Simulation of a galaxy clustert = 0.38 Myr
t = 13.7 Gyr
Dolag, Borgani, Murante & Springel 2008
Clusters form at the nodes of the cosmic web and can be usedas a tool to understand the physical state of diffuse baryons.
17/06/2009 – p. 2
IntroductionObservations (⇒), Simulations (⇐) and the role of~B:
DSSVLA
Galaxies (optical, radio):⇒ Interaction with the ICM
⇐ Galaxies in dense environment(stripping , distribution of metals)
⇐ Magnetic fieldseeding(outflows)
Snowden, ROSAT
ICM (X-ray, thermal bremsstrahlung):⇒ Dynamical state of ICM
⇐ Non thermalpressuresupport
⇐ Turbulence, viscosity, shocks
Deiss, Effelsberg
ICM (radio, synchrotron radiation):⇒ Distribution of ~B, CRs (diffuse + RM)
⇐ Evolution andbuildup of ~B
⇐ Accelerationandpropagation of CRs17/06/2009 – p. 2
Faraday Rotation (RM)
9h15m41.0s9h15m41.5s9h15m42.0s9h15m42.5s9h15m43.0s
-11:53:00
-11:52:50
-11:52:40
RA
DEC
-2000 0 2000 4000 6000 (RAD/M/M)
50 100 150 200
200
400
600
-100 -50 0 50 (counts)
3C449 Hydra
Feretti et al. 1999
Taylor & Perley 1993
150
kpc
20 kpc
High quality Rotation Measure maps across the lobes of thecentral radio source in 3C449 (left) and Hydra (right).
• Cool core versus cluster wide turbulence / fields structure?• Origin of cosmological magnetic fields ?• Extension, structure and evolution of magnetic fields ?
17/06/2009 – p. 3
Faraday Rotation (RM)B(r) = B0
(
1 + (r/rc)2)−1.5µ
, |Bk|2 ∝ k−n
2 MpcA119
Murgia, Govoni, Feretti, Giovannini, Dallacasa, Fanti, Taylor & Dolag 2004
⇒ B0 = 5µG n = 2 µ = 0.517/06/2009 – p. 3
Faraday Rotation (RM)Coma
3 Mpc
Bonafede, Feretti, Govoni, Murgia, Giovannini, Dolag & Taylor 2009
n
1.0
1.5
2.0
2.5
3.0
3.5
10 2 3 4 5
100 200 300 400 500maxλ
6
17/06/2009 – p. 3
Radio Halos (synchrotron)
Feretti 1999
Radio Halo
Radio Relic
1 Mpc
Dolag & Ensslin 2000
Cluster widediffuse synchrotron emissionconnected tomerger events,periferal emission directly connected toshocks.
• Radio halo: Turbulence, shocks, secondary ?• Relics: Primary from shocks or compressed radio plasma ?
17/06/2009 – p. 4
Simulation Network
−4.5 −4.0 −3.5 −3.0 −2.5 −2.0 −1.5
Virgo
Hydra
Perseus
Coma
Centaurus
2log( )ρ /cm ][g
−11.0−13.0−15.0−17.0−19.0−21.0−23.0
λ γlog( )γ 2[ /cm /s/arcmin ]2
Virgo
Hydra
Perseus
Coma
Centaurus
−11.0−13.0−15.0−17.0−19.0−21.0−23.02log(Lx) [erg/cm /s/arcmin ]2
−11.0 1.0−2.0−5.0−8.0−17.0 −15.0
log(P )ν [mJy/arcmin ]2
1.0−1.0−3.0−5.0−7.0−9.0−11
log(|B|) µ[ G]
Perseus
Hydra
Coma
A3627
Virgo
Pavo
Centaurus
(M)δMechanism
???Efficiency
CR−p CR−e
−3.0−4.0−5.0 −2.0 −1.0 0.0 1.0
log( )T [keV]
−9.5 −8.5 −7.5 −6.5 −5.5 −4.5log(Y)
−10.5
Temperature
Density
Structure Formation
ICs (Cosmology)
Turbulence
−ray SBγ Radio SB
Cosmic Rays
AGN ?
Observables
X−ray SB
thermal SZ
Dolag, Hansen, Roncarelli & Moscardini 2005 Dolag, Grasso, Springel & Tkachev 2004/2005Donnert, Dolag, Cassano & Brunetti 2009
Seed Magnetic Field
Magnetic Field Evolution
Shock Statistics
UHECR−
Feedback ?Star Formation ? Dissipation ?
Numerics ?Resolution ?
Magnetic Field
Magnetic Pressure
Compression
Coupling to Star Formation
Viscosity ?Numerics ?Sub−Grid Model ?
Description ?Diffusion ?
Detection ?Numerics ?
Deflection17/06/2009 – p. 5
MHD with SPH
Why SPH ?
• Perfect self gravity⇒ excellent to capture structure
formation
• Lagrangian⇒ excellent advection
• Highly adaptive⇒ large dynamical range
• Low dissipation⇒ no numerical mixing
• Efficient⇒ large simulations
• Simple⇒ allows to include various physical processes
• Ideal MHD:+ Induction equation + Lorenz force⇒ Many details to obtain stable and reliable
implementation
17/06/2009 – p. 6
MHD with SPHCode verification in 1D shock tube tests (Ryu & Johns 1995)(Dolag et al. 1999, 2001, 2005) ...Code verification in various 2D tests
Athena
Art. Dissipation B smooth
SPH−MHD Athena
Art. Dissipation
SPH−MHD
B smooth
Magnetic field in the vortex (Orszag & Tang 1979) and the rotor (Balsare
& Spicer 1999) test problem. Results for Anthena (top left) andSPH-MHD runs (Dolag & Stasyszyn 2008).
17/06/2009 – p. 6
Cosmological MHD simulations
Origin• Primordial• Battery• Dynamo (Turbulence)• Stars• Supernova• Galactic Winds• AGN, Jets• Shocks Rees 1994
+ further amplification bystructure formation
- dissipation ?
17/06/2009 – p. 7
Cosmological MHD simulations5 Mpc
Dolag et al. 1999/2002
First cluster MHD simulations (Dolag et al. 1999/2002)• Simulations reproduce the radial shape of the RM signal
⇒ Magnetic power spectrum of clustersn ≈ 2.3 − 3.1• Magnetic field configuration driven by cluster dynamics
⇒ Initial magnetic fieldstructure not important• Initial fields of≈ (0.2 − 1) × 10−11 G are sufficient
⇒ in range formany modelsfor magnetic seed fields17/06/2009 – p. 7
Cosmological MHD simulations
(counts)
RA
DEC
(RAD/M/M)
684 kpc
68.4 Mpc
6.84 Mpc
684 Mpc
RM
SimulationObservation
Feretti et al. 1999
3C449
“Zoomed” cluster simulations (Dolag & Stasyszyn 2008)17/06/2009 – p. 7
Cosmological MHD simulations
⇒ Several times confirmed since early work⇒ Generic feature from structure formation
17/06/2009 – p. 7
Cosmological MHD simulations
But: Central part steepens strongly with resolution.⇒ Resolutionis important
17/06/2009 – p. 7
Cosmological MHD simulations
Attention : Also depends strongly on dissipation⇒ Numerical dissipationis important
17/06/2009 – p. 7
Cosmological MHD simulations
(counts) (counts) (counts) (counts)
RA
DEC
(RAD/M/M)
−3 3 −30 30 −70 70 −600 600
3000x220x130x10x3C449
Feretti 1999 Dolag 2005 Dolag 2006 Dolag 2009 Dolag 2009
(counts)70−70
Observed and simulated RM maps up to highest resolutionsimulation: MHD, 20 Million particles withinRvir,mDM = 107M⊙/h, ǫGrav = 1kpc/h(work in progress).
17/06/2009 – p. 7
Cosmological MHD simulations
3C440 (Feretti 1999)220x (Dolag 2009)
3000x (Dolag 2009)
130x (Dolag 2006)10x (Dolag 2005)
Structure function derived from observed and simulated RMmaps up to highest resolution simulation: Indication for need ofmagnetic dissiation (work in progress).
17/06/2009 – p. 7
Origin of Magnetic Fields
Seeding from galactic outflows (Donnert, Dolag et al. 2008)17/06/2009 – p. 8
Origin of Magnetic Fields
Different wind parameters (Donnert, Dolag et al. 2008)17/06/2009 – p. 8
Propagation of UHECRs
Trajectories of Cosmic Rays diffusing through the cluster core(Rordorf, Grasso & Dolag 2004)
17/06/2009 – p. 9
Propagation of UHECRs
Perseus
Coma
Virgo
HydraCentaurus
Pavo
A3627
0.0 1.0 2.0 3.0 4.0 5.0 [Degrees]
Full sky deflection signal for4 × 1019eV Cosmic Rays withoutlosses, using a sphere of 110 Mpc radius andB0 = 10−5µG(Dolag, Grasso, Springel & Tkachev 2004)
17/06/2009 – p. 9
Propagation of UHECRs
Perseus
Coma
Virgo
HydraCentaurus
Pavo
A3627
0.0 0.2 0.4 0.6 0.8 1.0 [Degrees]
Full sky deflection signal for4 × 1019eV Cosmic Rays withoutlosses, using a sphere of 110 Mpc radiusB0 = 0.2 × 10−5µG(Dolag, Grasso, Springel & Tkachev 2005)
17/06/2009 – p. 9
Propagation of UHECRs
Perseus
Coma
Virgo
HydraCentaurus
Pavo
A3627
0.0 0.1 0.2 0.3 0.4 0.5 [Degrees]
Full sky deflection signal for4 × 1019eV Cosmic Rays withoutlosses, using a sphere of 110 Mpc radius from galactic outflows(Just for you !)
17/06/2009 – p. 9
Propagation of UHECRs
Sky coverage of deflection signal for4 × 1019eV Cosmic Rayswithout losses, using a sphere of 110 Mpc radius for all models(Also just for you !)
17/06/2009 – p. 9
Propagation of UHECRs
Sky maps of UHECRs emitted uniformly from M87 with 1000(upper right), 100, 10 and 1 EeV (lower left)(Dolag, Kachelriess, Semikoz 2008), see talk by Dimitri Semikoz.
17/06/2009 – p. 9
Investigating magnetic fieldsRotation Measure:
RM ∝
∫
ne B‖ dl
⇒ additional proportionality to density
⇒ not very good for low density regions
Also background/foreground subtraction not trivial for next
generation of instruments like LOFAR, SKA or EVLA !
Other methods:
• Propagation of UHECRs (this talk)
• Blazar halos(Dolag, Kachelriess, Ostapchenko & Tomas 2009)
(see talk by Dimitri Semikoz)
• Dynamics in structure formation !
17/06/2009 – p. 10
Investigating magnetic fieldsGalaxy formation studies with RAMSES:
Teyssier 2009
17/06/2009 – p. 10
Investigating magnetic fieldsCosmological simulation with Gadget:
Bini = 10−5µG, work in progress,(Stasyszyn & Dolag 2009)
17/06/2009 – p. 10
Conclusions
• Predicted magnetic field structure reflects formationof galaxy clusters
• Galactic outflows are valid sources for cluster fields• Predicted (complex) field structure in galaxy clusters
is compatible with RM measures• Filaments might host remaining signatures of magnetic
field origin• UHECR propagation very promising
⇒ Pointing back to sources might be possible⇒ Complications from propagation in nearby clusters⇒ non defection of UHECRs measure small~B-fields
• Blazar halos allow to probe even lower~B-fields⇒ see talk by Dimitri Semikoz
17/06/2009 – p. 11
S.O.S
S.O.S
B
S.O.S
S.O.S
Stars
Radio Emission
hard/soft X−RayRadio Ghosts
Sharp Edges (cold fronts !)
Cooling
Some Baryonic Matter
Lots of Dark Matter
Turbulence
Thermal Conduction
Lots of Dark Energy ?
EUV excess ?
Do
we u
nd
ersta
nd
ou
r "
wo
rld
" !?
Galaxy clusters as physics laboratory:
Thermal Emission
WHIM
17/06/2009 – p. 12
Comparison Project
17/06/2009 – p. 13
Comparison Project
z=0.25
GadgetENZOz=1.0 z=0.5
z=0.25 z=0.11
z=1.0
z=0.11
z=0.5
17/06/2009 – p. 14
Comparison Projectz=1z=1
Gadgetz=0.5
z=0.11z=0.25 z=0.25
z=0.5
z=0.11
ENZO
17/06/2009 – p. 14
Comparison Project
17/06/2009 – p. 14
Turbulence in ClustersOld viscosity scheme New viscosity scheme
• Instabilities less damped (e.g. Kelvin-Helmholtz).
⇒ Inset of turbulence
⇒ Enlarged energy-fraction in gas velocity
Dolag, Vazza, Brunetti, Tormen & Springel 2004
17/06/2009 – p. 15
Turbulence in Clusters
0 0.0001 0.0002 0.0003 0.0004 dT/T
200 400 600 800 1000
200
400
600
800
1000
g8.gas.a.z
0 0.0001 0.0002 0.0003 dT/T
200 400 600 800 1000
200
400
600
800
1000
g8.gas_nv.a.z
Standard (left) and reduced (right) Viscosity, Compton-y map
17/06/2009 – p. 16