Early Polarization Science with ASKAP – Galactic Pole Takuya Akahori Sydney Institute for Astronomy (SIfA), The University of Sydney, Australia JSPS Postdoctoral Fellow for Research Abroad, Japan with B. M. Gaensler, and the POSSUM Collaboration ATNF, Australia ASKAP Early Science Workshop

Continuum Polarization Observation  Cosmic Magnetism Impossible to know our universe without knowing Cosmic Magnetism 2 CMB Polarization Inflation theory QUIET, PolarBeaR, LiteBIRD CMB Polarization Inflation theory QUIET, PolarBeaR, LiteBIRD Key Sciences in Modern Cosmology Epock of Reionization Dark age / First stars MWA, LOFAR, SKA Epock of Reionization Dark age / First stars MWA, LOFAR, SKA “Foreground” ・・・ SFR, IMF Turbulence ISM, SNR Spiral/Halo Instabilities Milky Way Cosmology UHECRs IGM Environment Feedback AGN Population Morphology Galaxies

Observation toward Galactic Pole  Best to study the IGMF ›Galactic RM depends on b, and is smallest toward the poles 3 NVSS-RM (Schnitzeler 10) RM Galactic latitude Galactic Halo Mao+ (10)Stil+ (11)TA+ (13)TA, Ryu (10;11) IGMF +0.0±0.5 rad/m 2 ~0.00±0.02 µG +6.3±0.5 rad/m 2 ~0.31±0.02 µG MRI Parker Loop

The IGMF in the Cosmic Web  Big Mystery and New Frontier ›What is the origin and nature of the IGMF? -Practically, radio polarimetry is a unique probe -RM~1-10 rad/m 2 through filaments? (TA, Ryu 10;11) 4 Coma cluster (Kim+ 89) AMR-MHD initial uniform B~10 pG (Dubois & Tessier 08) (M)HD Biermann battery & turbulence dynamo (Ryu+ 98; Ryu+ 08) SPH-MHD magnet-gas injection (Donnert+ 09; Stasyszyn+ 10) log B(µG) log ρ/ρ log ρ/ρ log ρ/ρ log B(µG) log B(µG)

Progress of Extragalactic RM Studies  Intrinsic, Intervening, and the IGMF ›Multiple RMs along LoSs ›Which RM component contributes to the observed RM? › And how? 55 Solid: RM 6cm Dashed: RM 21cm Bernet+ (12) Hammond+ (12) Intervening galaxies Large Intrinsic Small Intrinsic No intervening galaxies Large Intrinsic Small Intrinsic This talk Challenge to discover RM of the IGMF (1-10 rad/m 2 ) Bryan Gaensler’s Talk Thermal emvironment of active galaxies. Galaxy evolution over cosmic time. Turbulence properties and covering fraction of absorbers <~50%? [1,2] σ INT ~5-12 rad/m 2 ? [2] [1] Zhu, M’erard 13, [2] TA, Gaensler, Ryu in prep. Radio GalaxiesQuasars “risk hedge”

Is the IGMF good for Early Science?  Yes. Statistics of RM ›RM of the IGMF could be extracted (D>10) 6 TA, Ryu 10;11; TA et al. 13; TA, Gaensler, Ryu, in prep. Previous Observation ASKAP-12, 6 hours FoV = 900 deg 2 toward the South GP ー Model IGM ー Mock Obs. ー Residual RM FoV = 900 deg 2 toward the South GP ー Model IGM ー Mock Obs. ー Residual RM Galaxy filter High-z filter High-pass filter Mock Obs. Map Extracted Map

Is the IGMF good for Early Science?  Yes. Synthesis of RM ›Null IGMF could be excluded at 2-3σ signif. ( MHz) 7 TA+ submitted; Ideguchi, TA+, submitted ASKAP-12, 1 hour, 1 mJy source, RM IGMF =10 rad/m 2 ー MHz ー MHz ー ( ) MHz ー MHz ASKAP-12, 1 hour, 1 mJy source, RM IGMF =10 rad/m 2 ー MHz ー MHz ー ( ) MHz ー MHz Mock Obs. Spectrum Model RM Synthesis QU-fitting 1σ

Is the IGMF good for Full Science?  Of course, Yes! ›Statistics of RM  Structure Function ›Synthesis of RM  RM~a few rad/m 2 8 TA, Gaensler, Ryu, in prep.; TA+ submitted; Ideguchi, TA+, submitted ー ASKAP-12 ー ASKAP-18 ー ASKAP-36 3σ 1σ ASKAP-12, 6 hours FoV = 900 deg 2 toward the South GP ー Model IGM ー Mock Obs. ー Residual RM FoV = 900 deg 2 toward the South GP ー Model IGM ー Mock Obs. ー Residual RM ASKAP-36, 15 hours 1σ

Summary: Continuum Polarization Observation toward Galactic Pole The IGMF in the cosimc web is a mystery & frontier in cosmology Practically, radio polarimetry is a unique probe of the IGMF Scientific Backgrounds A survery toward the Galactic pole is the best to study the IGMF We pay attention to the LoS toward which the RM is predominant Target with ASKAP-12 Survery specification: continuum pol. survey (Gaensler et al.) 6 hours per pointing is required to extract RM due to the IGMF 700 – 1800 MHz is required to exclude null IGMF at 2-3 σ signif. Full survery with ASKAP-36 would provide further improvements Technical requirement: the POSSUM pipeline + QU-fit (installed) Requirement and Feasibility 9

Questions and Answers 1 ›What unique discovery space can we explored with ASKAP-12? -The Intergalactic magnetic field (IGMF) in the cosmic web ›What are the minimum requirements in your area of interest? -6 hours per pointing (10 RMs per deg 2 ), 2-3 x 300 MHz bands ›What science tipics could be tackled with a short amount of observing time (1 hour – 1 week)? -We challenge to discover RM due to the IGMF in the cosmic web (10 rad/m 2 ) ›Are there short observations that can tackle a number of different topics simultaneously? -RMs of intrinsic, intervening, and the IGMF could be tackled with our proposing continuum polarization survey ›What could be achieved with a longer survery? -Structure function of RMs, much more RMs (<10 rad/m 2 ) 10

Questions and Answers 2 ›What is the potential for commensal science? -The intergalactic magnetic field (IGMF) in the cosmic web ›How does ASKAP-12 compare with other existing telescopes? -A ~1000 MHz band is unique ›What is the likely science impact of the observations? -May prove turbulence dynamo in the cosmic web, affects CR and γ-ray studies ›Are observations “high-risk” or “low-risk” in terms of implementations? -Major Risks: N of polarized sources, optical counterpart (absorption/redshift) ›What are the likely minimum requirements with respect to observing time? -6 hours per pointing (in order to reach 40 µJy/beam) ›Do the observations have advanced data processing, imaging or calibration requirements? -Yes. RM synthesis and QU fitting (but are already installed in the POSSUM pileline) ›Are there any requirements that are different from those of the ASKAP SSPs or the intended specifications or deliverables? -Yes. 11

Expected number of polarized sources 12 Calculator of the number of polarized sources (Excel Object, double-click to open) dN/dS: Wilman et al. (2008), O’Sullivan et al. (2008) ASKAP-12: Bryan’s handout Confusion Limit: EMU_Configuration_Studies_for_ASKAP_2013mar16b.pdf

Expected number of polarized sources 13 Calculator of the number of polarized sources (Excel Object, double-click to open) dN/dS: Wilman et al. (2008), O’Sullivan et al. (2008) ASKAP-12: Bryan’s handout Confusion Limit: EMU_Configuration_Studies_for_ASKAP_2013mar16b.pdf

Expected number of polarized sources 14 ›Wilman+ 08 ›O’Sullivan+ 08

Model and Calculation μ RM [rad/m 2 ] σ RM [rad/m 2 ] INT01-10 IGM01~8 EXG00* ISM+6~5 ERR01 15 Akahori, Gaensler, Ryu, in prep. * rad/m 2. Instead, 50% of available sources are removed. 900 deg 2 toward the South Pole

Statistics Analysis: Probability Distribution 16 Akahori, Gaensler, Ryu, in prep. ー Model IGM ー Mock Obs. ALL ー Residual RM We get similar feasibility for 30 deg 2 FoV

Statistics Analysis: Structure Function 17 ー Model IGM ー Mock Obs. ALL ー Residual RM Akahori, Gaensler, Ryu, in prep. We get similar feasibility for 30 deg 2 FoV

Statistics Analysis: Error 18 Akahori, Gaensler, Ryu, in prep. ›Source density, D=100, Redshift threshold, zc=2.0, Smoothing angle, θc=5.0

Model and Calculation ›Conditions -Use sources with no intervening galaxies (nn absorption feature) -RM at the source but located out of radio-emitting regions is 0 ›Fisher Analysis ›Two Gaussian model -8 parameters 19 Galactic diffuse emission IGMF↓ Quasars Radio Galaxies Test run: RM IGMF =10 rad/m 2, fd=fc=1 mJy, 1 hour observation, Φd=9 rad/m 2, δΦd=3 rad/m 2, θd=π/4, δΦd=0.4 rad/m 2 Ideguchi, Takahashi, Akahori, Kumazaki, Ryu, submitted

Result: MHz Confidence Regions (1-σ significance) ー ASKAP-12 ー ASKAP-18 ー ASKAP Ideguchi, Takahashi, Akahori, Kumazaki, Ryu, submitted