Early Polarization Science with ASKAP – Galactic Pole Takuya Akahori Sydney Institute for...
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Transcript of Early Polarization Science with ASKAP – Galactic Pole Takuya Akahori Sydney Institute for...
Early Polarization Science with ASKAP – Galactic PoleTakuya AkahoriSydney Institute for Astronomy (SIfA), The University of Sydney, Australia
JSPS Postdoctoral Fellow for Research Abroad, Japan
with B. M. Gaensler, and the POSSUM Collaboration
2013/8/5 @ ATNF, AustraliaASKAP Early Science Workshop
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Continuum Polarization Observation Cosmic Magnetism
Impossible to know our universe without knowing Cosmic Magnetism
CMB PolarizationInflation theory
QUIET, PolarBeaR, LiteBIRD
Key Sciences in Modern CosmologyEpock 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
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Observation toward Galactic Pole Best to study the IGMF
› Galactic RM depends on b, and is smallest toward the poles
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/m2
~0.00±0.02 µG
+6.3±0.5 rad/m2
~0.31±0.02 µG MRI
Parker Loop
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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/m2 through filaments? (TA, Ryu 10;11)
Coma cluster(Kim+ 89)
AMR-MHDinitial uniform
B~10 pG(Dubois & Tessier 08)
(M)HDBiermann battery & turbulence dynamo(Ryu+ 98; Ryu+ 08)
SPH-MHDmagnet-gas injection
(Donnert+ 09;Stasyszyn+ 10)
log B(µG)-1
-2
-3
-4
log ρ/ρ0
0 2 4 6 log ρ/ρ0
0 1 2 3 4
log ρ/ρ0
0 1 2 3 4
log B(µG)-0-1-2-3-4
log B(µG)-0
-2
-4
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Progress of Extragalactic RM Studies Intrinsic, Intervening, and the IGMF
› Multiple RMs along LoSs
› Which RM component contributes to the observed RM?
› And how?
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Solid: RM 6cmDashed: RM 21cm
Bernet+ (12) Hammond+ (12)
Intervening galaxies
Large Intrinsic
Small Intrinsic
No intervening galaxies
Large Intrinsic
Small Intrinsic
This talkChallenge to discover RM of the IGMF (1-10 rad/m2)
Bryan Gaensler’s TalkThermal emvironment of active galaxies. Galaxy evolution over cosmic time. Turbulence properties and covering fraction of absorbers
<~50%? [1,2]
σINT~5-12 rad/m2? [2]
[1] Zhu, M’erard 13, [2] TA, Gaensler, Ryu in prep.
Radio Galaxies Quasars
“risk hedge”
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Is the IGMF good for Early Science? Yes. Statistics of RM
› RM of the IGMF could be extracted (D>10)TA, Ryu 10;11; TA et al. 13; TA, Gaensler, Ryu, in prep.
Previous Observation ASKAP-12, 6 hours
FoV = 900 deg2 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
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Is the IGMF good for Early Science? Yes. Synthesis of RM
› Null IGMF could be excluded at 2-3σ signif. (700-1800 MHz)TA+ submitted; Ideguchi, TA+, submitted
ASKAP-12, 1 hour, 1 mJy source, RMIGMF=10 rad/m2
ー 1150-1450 MHz ー 700-1000 MHz ー (700-1000+1150-1450) MHz ー 700-1800 MHz
Mock Obs. Spectrum
Model
RM Synthesis
QU-fitting
1σ1σ
1σ
1σ1σ
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Is the IGMF good for Full Science? Of course, Yes!
› Statistics of RM Structure Function
› Synthesis of RM RM~a few rad/m2
TA, Gaensler, Ryu, in prep.; TA+ submitted; Ideguchi, TA+, submitted
ー ASKAP-12ー ASKAP-18ー ASKAP-36
ー ASKAP-363σ 3σ
1σ
ASKAP-12, 6 hours
FoV = 900 deg2 toward the South GPー Model IGM ー Mock Obs. ー Residual
RMASKAP-36, 15 hours
1σ1σ
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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