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Takuya Akahori Chungnam National University

Exploring Faraday Rotation Measure due to the Intergalactic Magnetic Field with the Square Kilometer Array. Takuya Akahori Chungnam National University. Contents. Introduction Faraday Rotation Measure (RM) due to the Intergalactic Magnetic Field (IGMF) Part 1. present-day local universe

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Takuya Akahori Chungnam National University

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  1. Exploring Faraday Rotation Measure due to the Intergalactic Magnetic Field with the Square Kilometer Array Takuya Akahori Chungnam National University SKA-JP Workshop 2010@NAOJ

  2. 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 submitted Akahori, SKA-Japan sub-SWG “Cosmic Magnetism”, Chap. 4 SKA-JP Workshop 2010@NAOJ

  3. Introduction: Baryon in our Universe Baryon Phase • ICM (>107K) • WHIM (105-7K) • Others Intra-Cluster Medium Warm-Hot Intergalactic Medium Baryon Phase Diagram from cosmo. simulation (Piro+ 07) Magnetized? Inter-Galactic Magnetic Field IGMF Ionized Medium ICM/WHIM SKA-JP Workshop 2010@NAOJ

  4. Introduction: IGMF and RM Evidences of Magnetization • ICM: RM ~100 [rad m-2] IGMF ~1-10 [μG] • Kolmogorov? (Vogt & Ensslin 05; Guidetti+ 08; Bonafede+ 10) • WHIM: RM < 10 [rad m-2] ? IGMF ~ ? Where is the large-scale structure? RM through the ICM Govoni+ (10) All sky RM map Taylor, Stil, Sunstrum (09) IGMF remains largely unknown SKA-JP Workshop 2010@NAOJ

  5. 100 h-1 Mpc 10-4μG |B| 10μG Ryu+ (08) Model: Our Model for the IGMF • Goal:Predict RM of WHIM & test it by future obs. • Method: Simulation of the cosmological structure formation + turbulence dynamo model (Ryu+ 08) • MHD…still hard to treat evolution of turbulence and amplification of the IGMF correctly turbulence dynamo model 1. vorticity energy εw 2. regard εw as εturb 3. εB/εturb=f(t/teddy) 4. B=(8πεB)1/2 Energy density ICM Ryu+ (08) WHIM Cho & Ryu (09) time [teddy] SKA-JP Workshop 2010@NAOJ

  6. 1 Present-day Local universe: Profiles 2.0 1.0 0.0 -1.0 -2.0 Log10 |RM| [rad m-2] • RM:~100 (GCs),~10 (Groups),~0.01-1 (filaments) • RM: a random walk process, peaked at the center -50 -25 0 25 50 [h-1Mpc] SKA-JP Workshop 2010@NAOJ

  7. 100 h-1 10 h-1 1 h-1Mpc 10 h-1 1 h-1Mpc 1 Present-day Local Universe: Statistics PDF of |RM| for WHIM (105 K<Tx<107 K) Tx: emissivity weighted temperature. Black: 3×16 runs,Red: average,Blue: best-fit ・Lognormal profile of PDF ・rms ~ 1.4 [rad m-2] for WHIM 2D power spectra of RM and the projected IGMF Black: 3×16 runs, Red: average ・Peaked at ~Mpc scale ・PRM(k) traces PB||,proj(k) SKA-JP Workshop 2010@NAOJ

  8. z=0.1 0.3 0.5 1.0 3.0 5.0 Log |RM| [rad m-2] 2 Cosmological Effects: RM Stacking Willman+ (08) • |RM| increases with integrating RM along LOS Simulation boxes are stacked up to z=5 Redshift distribution of radio sources are considered SKA-JP Workshop 2010@NAOJ

  9. 2 Cosmological Effecs: rms Value Subtl. of ICM in the integration temperature Tx=4keV Tx=1.5keV 107K Line of sight ALL 1Mpc CLS TM7 Average of 200 runs Subtl. of ICM after the integration ALL Map Pixcels w Tx>107K & Sx>10-8 e/s/cm2/sr TS8 ALL Map Pixcels w Tx>107K & Sx>10-10e/s/cm2/sr TS0 SKA-JP Workshop 2010@NAOJ

  10. 2 Cosmological Effects: Statistics Average of 200 runs ~0.2º • PDF of |RM| follows thelog-normaldistribution • Power spectrum peaks at ~0.2º scale TM7 z<5 z<0.3 z<0.05 1.4º 0.14º SKA-JP Workshop 2010@NAOJ

  11. Intergalactic? Galactic 10º-100º 0.2º 2 Cosmological Effect: Structure Function • Flat SF profile in ~0.1º-10º 2nd order SF ALL TS8 TS0 Average of 200 runs 0.1º 1º 10º 2nd order SF (Mao+ 10) SKA-JP Workshop 2010@NAOJ

  12. Intrinsic RM Intrinsic + Galactic Galactic RM Filtered RM FFT FWT 3 Galactic Foreground: Concept of Analysis • Galactic foreground RM of order ~10 [rad m-2] is a serious contamination Remove the large scale component 0.2º 10º-100º High-pass filter Galactic Contamination? SKA-JP Workshop 2010@NAOJ

  13. 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 Our estimated RM could be tested with the SKA A concept design for SKA Phase 1 (Garrett+ 10) SKA-JP Workshop 2010@NAOJ

  14. 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) SKA-JP Workshop 2010@NAOJ

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