Takuya Akahori Chungnam National University
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Transcript of Takuya Akahori Chungnam National University
2010.11.4-5 SKA-JP Workshop 2010@NAOJ Akahori 1/14
Exploring Faraday Rotation Measure due to the Intergalactic Magnetic Field w
ith the Square Kilometer Array
Takuya AkahoriChungnam National University
2010.11.4-5 SKA-JP Workshop 2010@NAOJ Akahori 2/14
Contents
• Introduction
• Faraday Rotation Measure (RM) due to the Intergalactic Magnetic Field (IGMF)– Part 1. present-day local universe– Part 2. cosmological effect– Part 3. galactic foreground
• Summary and Future
References:Akahori, Ryu (2010), ApJ, 723, 476ー (2010) to be submittedAkahori, SKA-Japan sub-SWG “Cosmic Magnetism”, Chap. 4
References:Akahori, Ryu (2010), ApJ, 723, 476ー (2010) to be submittedAkahori, SKA-Japan sub-SWG “Cosmic Magnetism”, Chap. 4
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Introduction: Baryon in our Universe
Baryon PhaseBaryon Phase
• ICM (>10ICM (>1077K)K)
• WHIM (10WHIM (105-75-7K)K)
• OthersOthersBaryon Phase Diagram from cosmo. simulation (Piro+ 07)
Intra-Cluster Medium
Warm-Hot Intergalactic Medium
Ionized MediumICM/WHIM
Magnetized?Inter-Galactic Magnetic Field
IGMF
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Introduction: IGMF and RM
Evidences of MagnetizationEvidences of Magnetization• ICM: ICM: RM ~100 [rad mRM ~100 [rad m-2-2] ] IGMF ~1-10 [μG]IGMF ~1-10 [μG]
– Kolmogorov? (Vogt & Ensslin 05; Guidetti+ 08; Bonafede+ 10)
• WHIM: WHIM: RM < 10 [rad mRM < 10 [rad m-2-2] ?] ? IGMF ~ ? IGMF ~ ?
RM through the ICMGovoni+ (10) All sky RM map
Taylor, Stil, Sunstrum (09)
IGMF remains largely unknown
Where is the large-scale structure?
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Model: Our Model for the IGMF
• Goal: Predict RM of WHIMPredict RM of WHIM & test it by future obs. • Method: Simulation of the cosmological structure fo
rmation + turbulence dynamo model (Ryu+ 08)turbulence dynamo model (Ryu+ 08)– MHD…still hard to treat evolution of turbulence and amplification of the IGMF correctly
time [teddy]
En
erg
y d
en
sity
WHIM
ICM Ryu+ (08)10-4μG |B| 10μG
100 h-1 Mpc
Ryu+ (08)
Cho & Ryu (09)
turbulence dynturbulence dynamo modelamo model
1. vorticity energy εw
2. regard εw as εturb
3. εεBB/ε/εturbturb==f(t/tf(t/teddyeddy)) 4. B=(8πεB)1/2
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1 Present-day Local universe: Profiles
• RM: ~100 (GCs), ~10 (Groups), ~0.01-1 (filaments)• RM: a random walk process, peaked at the center
Log10 |RM| [rad m-2]
-50 -25 0 25 50[h-1Mpc]
2.0
1.0
0.0
-
1.0
-2.0
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1 Present-day Local Universe: Statistics
・ Lognormal profile of PDF・ rms ~ 1.4 [rad m-2] for WHIM
PDF of |RM| for WHIM (105 K<Tx<107 K)Tx: emissivity weighted temperature. Black: 3×16 runs, Red: average, Blue: best-fit
・ Peaked at ~Mpc scale・ PRM(k) traces PB||,proj(k)
2D power spectra of RM and the projected IGMFBlack: 3×16 runs, Red: average
100 h-1 10 h-1 1 h-1Mpc 10 h-1 1 h-1Mpc
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2 Cosmological Effects: RM Stacking
• |RM| increases with integrating RM along LOS
Simulation boxes are stacked up to z=5Redshift distribution of radio sources are considered
Willman+ (08)
z=0.1 0.3 0.5 1.0 3.0 5.0
Log |RM|[rad m-2]
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2 Cosmological Effecs: rms Value
[rad m-2]
RM of WHIM (in) 7-10RM of WHIM (after) 6-7
Subtl. of ICM after the integration
temperature
107K
Subtl. of ICM in the integration
Tx=4keVTx=1.5keV
ALL
CLS1Mpc
TM7
TS8ALLMap
Pixcels w Tx>107K& Sx>10-8 e/s/cm2/sr
TS0ALLMap
Pixcels w Tx>107K& Sx>10-10e/s/cm2/sr
Line of sight
Average of 200 runs
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2 Cosmological Effects: Statistics
• PDF of |RM| follows the log-normal distribution
• Power spectrum peaks at ~0.2º scale
1.4º 0.14º
~0.2º
z<0.05
z<0.3
z<5TM7Average of 200 runs
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2nd order SF (Mao+ 10)
2 Cosmological Effect: Structure Function
• Flat SF profile in ~0.1º-10º
2nd order SFALLTS8TS0
Galactic
10º-100º10º-100º
Intergalactic?
0.2º0.2º
0.1º 1º 10º
Average of 200 runs
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• Galactic foreground RM of order ~10 [rad m-2] is a serious contamination
3 Galactic Foreground: Concept of Analysis
Intrinsic + Galactic
Intrinsic RM
Galactic RM
High-pass filter
GalacticContamination?
10º-100º10º-100º0.2º0.2º
Remove the large scale componentRemove the large scale component
Filtered RM
FFT FWTFFT FWT
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Summary
RM in filaments is discussed using a model IGMF• Present-day local universe
– rms ~ 1 [rad m-2], lognormal, peak at ~Mpc • Cosmological effects
– rms ~ several [rad m-2], lognormal, peak at ~0.2º
• Galactic Foreground– High-pass filters (FFT/FWT) may work well
A concept design for SKA Phase 1 (Garrett+ 10)
Our estimated RM could be tested with the SKAOur estimated RM could be tested with the SKA
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Future
• Wide-band observation– RM ranges from ~0.1 to ~100 rad m-2
• Collaboration with galaxy community– Modeling of galactic foreground– Development of RM analysis
• Participation in projects – ASKAP/POSSUM– Japan SKA consortium SWG– Korea SKA consortium? Sofue, Machida, Kudo (10)