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Magnetic Jets and Lobes in Cosmological MHD
Hui Li Los Alamos National Laboratory
NSF/DOE Center for Magnetic Self-Organization (CMSO)
Collaborators:
H. Xu, D. Collins, S. Li, M. Morman
Overview of Observations and Magnetic Jet Model Results on 3D MHD Jet/Cluster Simulations Results on Cosmological MHD Jet/Cluster Simulations
Papers and Posters
1) Basic model: Li et al. ApJ, 2006
2) Jets in Static Clusters: Nakamura, Li, Li, ApJ, 2006, 2007
3) Comparison w. X-ray Bubbles: Diehl et al. ApJ, 2008
4) Comparison w. Herc A Observ: Nakamura et al. ApJ, 2008
5) Cosmological MHD Jet+Cluster Simulation: Xu et al. ApJL, 2008
6) Long-time evolution of magnetic bubble: Liu et al. ApJL, submitted
Both Steven Diehl and Hao Xu have posters at this meeting.
We are also looking for a postdoc in this area.
Hydra A (Wise et al.)
Jets and Lobes in Galaxy Clusters :Effects of ICM Dynamics ?
MS0735.6+7421 (McNamara et al.)
~ 400 kpc
~ 1 Mpc
Perseus (Fabian et al.)
~ 250 kpc
disk
Poloidal flux: ~ 104 (1014)2 ~ 1032 (G cm2) Toroidal flux: ~ (t) G cm2) Current: I ~ B R ~ 1018 A Mag. energy injection rate: dEmag/dt = Iz V - Ploss
Expansion: Iz(r,t), (r,t), and Ploss(r,t).
BH
Li et al. (2006)
Astrophysical Jets: Engine and Injection
€
λ =I polΨpol
r0QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Ipol
r0
Li (2008)
With Both Magnetic and Kinetic Injections
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Ipol
r0
€
Magnetic field and Momentum Injection :
Poloidal Flux (Br and Bz) : Ψinj = r2 exp(−r2 − k 2z2)
Toroidal Field (and poloidal current) : Bφ inj =αΨinj /r,
Magnetic Flux (energy) injection : ∂B
∂t= Binj(r,z) • γB (t)
Kinetic energy injection : ∂(ρv)
∂t= vinj(r,z) • γ v (t)
3D MHD SimulationsCluster: isothermal, hydrostatic (initially)
T = 4 keV, nc = 0.01 (1/cm3), Rc = 40 kpc; = 0.5
Jets in Static Clusters:
injection time: 40 Myr
injection magnetic energy: ~ 3x1060 ergs (~2.5x1045 ergs/s)
mass injection rate: < Msun / yr
Magnetic field and current distribution(as kinetic energy injection increases…)
EB = 2.6x1060 ergsEk < 2.6x1056 ergs
EB = 1.8x1060 ergsEk = 0.7x1060 ergs EB = 1.6x1060 ergs
Ek = 2.3x1061 ergs
Run A Run B Run C
Alfven Speed (run F)
Alfven speed (run E)
Flow Speed (run F)
Flow Speed (run E)
Radius
Vel
ocit
y
Sub-Alfvenicwith shear Supersonic
Azimuthally averaged velocity profile at z=3
Run E: without Ek injection Run F: with Ek injection
Comparison of Energy Evolution
Einj = EBinj
Einj=EBinj+EKinj
EB EB
Eth
Eth
EK
EKEg
Eg
Magnetic/Thermallog10 (eB/eth)
Magnetic/Kineticlog10 (eB/ek)
Run F: Jets/Lobes are mostly magnetically dominated
Estimating Magnetic Fields and Energy Density
€
Bφ ∝IzR
,
eB ∝1
R2,
EB ∝ ln(R /R0)
Rlobe
Measuring B: could be small in the main volume.
But magnetic energy containedin the central region is a sizablefraction of the total lobe.
Analysis of 64 Bubbles in 32 ClustersSee Poster by Diehl (Diehl et al. 2008)
magnetic
HydroAdiabatic expansion
Cosmology Ideal-MHD Code( )
( )
( )
velocitypeculiar proper :v pressures; density, comoving :B
v BBvB
vBBvv
vBBvvv
v
2
,,
212
1,
2
11
2
112
2
1
1
2
1)(
01
2
22
2
g
g
g
g
P
BPE
a
a
at
Ba
a
aEa
aBPE
at
E
aa
aBP
at
at
ρ
γρ
ρ
ρρρρ
ρρ
+−
+=−××∇=∂
∂
+Φ∇•−−=⎥⎦
⎤⎢⎣
⎡•−⎟
⎠
⎞⎜⎝
⎛++•∇+
∂
∂
Φ∇−−=⎥⎦
⎤⎢⎣
⎡−++•∇+
∂
∂
=•∇+∂
∂
•
••
•
Xu et al. (2008, method paper)
• Developed AMR+MHD and implemented in ENZO code.
• ENZO AMR+Hydro simulation:
h=0.7, m=0.3, b=0.026, λ=0.7, 8=0.928
• Volume: 256 Mpc/h
• Initial 1283 root grid from
z=30, followed with 8 level
refinements (~8kpc/h)
for magnetic fields.
Cosmological AMR+MHD Simulation(see H. Xu’s poster)
Cluster formation with an AGN feedback (Xu et al. 2008)
X-rayIntensity
QuickTime™ and ampeg4 decompressor
are needed to see this picture.
Heating the Cluster Core Region(see Hao Xu’s poster)
Change of inflow mass of clusters with and without AGN injection
T=36 Myr T=156 Myr
T=336 Myr T=670 Myr
Magnetic jet input at high redshiftMagnetically dominated jet input at a halo at z=3size: 80 Mpc comovingInjection B fields strength: 40 microgauss Halo properties:Rvir = 0.248462 (Mpc)Mvir = 3.04303e+13 (M_solar)Mvir (gas) = 1.51376e+12 (M_solar) Mvir (dm) = 2.89165e+13 (M_solar)
Summary Jets/lobes as magnetically dominated system with large current
“Flaring”/Lobe formation related to background ICM pressure profile (coupled with 3D MHD instability)
Lobe size determined by balance between external pressure and total current
Magnetic energy is gradually converted to thermal and kinetic energies of the jet/lobes
Morphology of jet/lobe is heavily influenced by background ICM dynamics, though magnetic fields crucial in maintaining the integrity of jets/lobes
Relic evolution, leading to magnetization of ICM/IGM