SKAで探る 背景クェーサー偏波の 吸収線系による解消 と宇宙磁場研究 Takuya Akahori Section of Future Project, Mizusawa VLBI Observatory, Japan 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 1 1. Square Kilometre Array Project 2. Depolarizing Intervening Galaxies
１. SKA Project Square Kilometre Array Project 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 2
1. SKA Project PI 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 CDR AA1 AA2 AA3 AA4 18 64 256 512 LOW 8+0 64+0 120+8 133+64 MID(SKA+MKT) SKA1 Construction Bid Risk S. SKA = HQ + Commissioning IGO Survey EPA SKA1 timeline Construction 691 M€ 2017 2 telescopes Observatory Project Overview 3Tbps 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 3 Site 5Tbps Data center Site Data center Jodrell Bank MID Observatory @SA SKA1=133 Dishes(15m) + 64 Dishes(13.5m) Max. 150km SKA2=2,000 Dishes(15m) Max. 3000km LOW Observatory @ AU SKA1＝512 stations (131k LPs) Max. 65km SKA2＝4880 stations (1,250k LPs) Max. 300km GHQ UK 12 SKA members
1. SKA Project multi-objective project researchers share investment KSP** PI** Open Sky 4% ~ ½ of China ~ KSP 4, PI 4/yr 4% can produce many results Status of Japan (papers) and students (PhD) Band5 GC pulsars MW-VLBI ISM magnetism LOW EoR deep transients pulsar Individual ◯ institutes 25% (submitted as category-A) 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. representative 4 5% cosmology 70% institutes 2. Fair Return 3. IGO SKA nations 1. Time Allocation ✕ n SKA members share 90%** of observing time n Japan’s Plan • 2-4% contribution (TBD) • NAOJ SKA promotion office Widefield & multi-mode à • An associate member n Expected Return • KSP/PI opportunities • Science/engineering promotions • Training of next generations • International presence and status
1. SKA Project ASKAP/MeerKAT/Parkes HCN CH 3 OH* HI (Galaxies) OH* Reionization, HI (Epoch of VERA/KaVA JVN MWA/LOFAR H 2 CO 43 22 15 6.7 1.6 1.4 1.0 0.3 Glycin, Alanin, Urea, ... H 2 O* Band 6 Cosmic Magnetism SKA Science Protostars Quasars Late-type Stars ?? GHz SETI AGN jets Radio galaxies Fast Radio Burst, Transients SiO* Pulsars , Magnetars Sun, Stars ICM, IGM, CGM Universe HOT Universe COLD NH 3 0.05 5c Science Objectives は正しい？ 見つかる？ ミッシングバリオンは 磁場と乱流の宇宙進化は？ Magnetism あった？ 原始に宇宙の非ガウス性は 銀河の水素量はどのくらい？ Cosmology アインシュタイン重力理論 ダークガス問題は解決？ 背景重力波は存在する？ Pulsars 進んだ？ 宇宙再電離はどのように 第一世代星の質量は？ EoR(HI) 5 Cosmic Shadow 2018 @ Ishigaki Is. 2018/11/24-25 Milky Way 銀河中心より向こう側は Band 5ab FRBの起源は何？ 3/4 Band 2 LOW Band 1 (GHz) Freq. 宇宙人はいる？ 重力波はどこから来た？ Transients どうなっている？ 系外にアミノ酸は存在？ 氷雪帯内の構造は？ 原始惑星系円盤の Star/Planet フィードバックの歴史は？ ブラックホールの成長と ジェットの構造は？ AGN Book 2015 Cosmic Dawn) HI (Milky Way)
1. SKA Project 65 km 26m x 27 15mｘ133 + 13.5m ｘ64 Array config. - 3本アーム 3本アーム コア + 3本アーム Max. baseline 120 km 36 km Science Specification 150 km A/T @ 0.1,1.4 GHz 0.6 5.6 2 15 Good Good Sensitivity Resolution 35m x 512 x 14, 57m x 13 31m x 48, 40m Antenna Φ・# 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 6 2010年代 2020年代 2010年代 2020年代 Telescope LOFAR SKA1-LOW JVLA SKA1-MID Site 欧州 ( 北半球 ) 豪州 ( 南半球 ) 米国 ( 北半球 ) 南アフリカ共和国 ( 南半球 ) Freq. (GHz) 0.03-0.22 0.050-0.35 0.058-50 0.35 - 15(24) A/T in 100 m 2 /K, larger is better SKA2
1. SKA Project NVSS(1) 1 2 -2 -3 -4 Taylor,TA+15 POSSUM(30) -1 SKA1* (230-450) SKA2 (5000) *4μJy/bm, 2″resolution (Johnston-Hollitt, TA+15) SKA Science Book 2015 0 10 Advantages JVLA 2018/11/28 NSPO 7 Luminosity function of linearly- polarized extragalactic sources HST SKA1 N [deg 2 ] -2 -3 -4 P [log mJy] 1000 100 1 SKA-TEL-SKO-0000818
2. DINGs Depolarizing Intervening Galaxies 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 8
2. DINGs WHIM and IGMF RM LSS Cosmic Shadow 2018 @ Ishigaki Is. TA+18a;18d TA & Ryu 10;11 QSO FRB LSS 2 1 0 -1 -2 [rad/m 2 ] 10 Mpc/h Mod. Gv.? Cosmic Baryon Budget WHIM? Galaxies, clusters, H I, Lyα, O VI Observation Std. Cosmology http://www.youtube.com/watch?v=8UzVi8MJolo Visualized by R. Kaehler 9 2018/11/24-25 = ∫n e B || dl Log 10 |RM| • Warm-hot intergalactic medium (WHIM) • In galaxy filaments. T~10 5-7 [K], n~10 -6 ‒10 -4 [cm -3 ] • Inter-galactic magnetic field (IGMF) • WHIM is most likely magnetized • RM ~ 1 rad/m 2 (local) and ~several rad/m 2 (∫dz, z=5)
1. Introduction TA+14b; TA18d Filter at ~1°-2° Bright sources? Cluster removal Use no-DING LoS Depolarization σ INT (z=2)~1 rad/m 2 High-z sources? ICM filter ERR filter ISM filter DIG filter INT filter RRM map RRM map TA+ in prep Find the signal of the IGMF 50% MgII 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 10 QSO/FRB σ INT =σ 0 (1+z) -2 σ 0 =10 rad/m 2 IGM TA+11 map ERR(ionosphere) σ ERR =1 rad/m 2 ISM TA+13 map ALL Map DING High-b is better Criteria of S X & T X
2. DINGs E-vector angles Faraday rotation Wavelength-independent depolarization no pol? １ 2 Beam Depolarization ν １ no pol? １ 2 １ Faraday rotation NVSS =45″, ASKAP ~10″, SKA1 Band2 ~1″ ν ２ ν ２ How DP arises? depolarization 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 11 Burns 66; Sokoloff+98 Arshakian & Beck 11 Differential Faraday rotation no pol? ν １ １ １ 2 Faraday rotation Bandwidth Depolarization no pol? 2
2. DINGs I ○ 1. Polarization fraction I & P have the same spectral indices. DP reduces P , so that P/I decreases in wavelength frequency P/I RM 951 sources I∝ν α , Π∝λ β α: slope of Stokes I(ν) β: slope of Pol. Frac. Π(λ) Farnes+14a P DP × large What DP induces? RM λ-dependent quantities 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 12 2. Faraday RM P through a larger RM is more depolarized than that through a smaller RM. DP biases RM. Bernet+ 12 Solid: 6cm (4.9 GHz) Dash: 21cm (1.4 GHz) Cumulative PDF of RM Small RM? small frequency n Two λ-independent quantities becomes
2. DINGs Intervening Galaxies Dependence on z, beam, frequency Why only “flat-type” shows excess RM? Why only “steep-type” shows large DP? Question/Motivation Farnes+14b Cumulative PDF of RM 143 sources flat-type 232 sources steep-type 13 Cosmic Shadow 2018 @ Ishigaki Is. 2018/11/24-25 • Steep-type sources • α Stokes I <= -0.7, unresolved lobes? • Large DP (β<0) • No clear RM from Mg systems • Flat-type sources • α Stokes I >= -0.3, AGN cores? • Weak DP (β~0) • 6.9 ± 1.7 rad/m 2 /DING at observer • • • à Let’s do simulations!
2. DINGs 14 100 pc σ rand 30 kpc this local grid RM dispersion for σ rand Local grids = turbulent fields Models of Galaxies Global grids = coherent fields 100 pc Cosmic Shadow 2018 @ Ishigaki Is. 2018/11/24-25 at the saturation stage of isothermal compressible MHD turbulence TA+13 • Global (coherent) components • Modified NE2001 (h=1.8 kpc) • Disk(ASS/BSS) + Toroidal + X/OFF • Local (turbulent) components • Given M, β, l coh ~10-15 pc, we input data • Wind components (minor) • Just incorporated. No figures, Sorry! l coherent << box size à Gaussian à Burn’s DP n e_reg (x,y,z) B _reg (x,y,z) M rms (x,y,z) β 0 (x,y,z)
2. DINGs the pol. angle ~50% MgII system of SDSS 6 kpc (0.5), 8 kpc (1.0) 1” ~ 2 kpc (z=0.1), of the source the redshift Consider 15 Cosmic Shadow 2018 @ Ishigaki Is. 2018/11/24-25 gradient RM is from Calculation beam offset Quasars (Zhu & M’enald 13) • Source • 1″ or 10″ size • Uniform • α I = α P = -1 • 100% pol. • DING • z, i, models, • Observation • Stokes Q, U • Classical style:
2. DINGs DING’s RM 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 16 ◯: 10”, z=0.1, dx=0 kpc ○ : 1”, z=0.5, dx= 5 kpc Mean：0-200 rad/m 2 Dispersion: 5-40 rad/m 2 • RM strongly depends on MF configuration
2. DINGs PDF & Pol. fraction 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 17 1”, z=0.5, dx=5 kpc • PDF of RM within a beam does not follow the Gaussian à the resultant DP does not follow the Burn’s law
2. DINGs 2018/11/24-25 DING’s DP 10-25% ●10”(lobe=steep) RM ~ 2-8 rad/m 2 DING’s DP ~10 % ◯1”(core=flat) ● 10” ◯ 1” 18 Cosmic Shadow 2018 @ Ishigaki Is. Farnes+14ab Monte-Carlo Simulations consistent with chosen randomly shape, offset are realizations RM < 1 rad/m 2 • 100k • Inclination, B- • Results • Freq. dependent • Trends broadly
2. DINGs Bias effect on RM the observed RM does not increase by 5! 2018/11/24-25 Cosmic Shadow 2018 @ Ishigaki Is. 19 z 8 rad/m 2 60 rad/m 2 Estimated DING’s RM z 10 rad/m 2 100 rad/m 2 Intrinsic DING’s RM • If we increase the intrinsic RM by 5 times, • The “effectiveness” is 0.5 ‒ 0.9 as func. of λ and z DING
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