国際SWGの報告(まとめ)	

竹内 努	
名古屋大学理学研究科素粒子宇宙物理学専攻	

宇電懇シンポジウム, 名古屋, 2013年12月19日	

1 SKA国際Science Working Group
1.1 国際SWGの構成
SKA office	

SWG	

Science director	

European P. S.
Deputy European P.
S.
CSIRO P. S.
AAVP V. S.

Science teamdelegate	Project scientist	

Deputy project
scientist	

Pulsars for
fundamental physics	

EoR and Dark Ages	

Cosmology	

HI surveys for galaxyevolution	

Continuum surveys	

Cradle of life	

Transients	

Cosmic magnetic fields	

Science Teams	1.2 国際SWGへの参加者
昨年12月に改組し、以下の8グループとなった。
1. Epoch of Reionization
2. HI surveys and galaxy evolution
3. Transients
4. Pulsars for fundamental physics
5. Continuum surveys
6. Cradle for life
7. Cosmology
8. Magnetic fields and polarization

井上、市來
竹内、平下今井高橋
赤堀、高橋それぞれのグループが、2-3ヶ月に1回ペースで電話会議。
重要な連絡はメールベース。	

1.3 最近の重要な話題
Document for top level science requirements
抜粋:
SKA1 will provide researchers with a general-purpose
astrophysics facility to permit state-of-the-art observations ofastronomical sources over a wide range of angular resolutions
between radio frequencies of 50 MHz and at least 3 GHz(within the context of an upgrade path to at least 20 GHz). Thefacility will be optimised for both large area surveys as well as
deep pointed observations and will provide point-source
sensitivity at least five times greater than currently existing
facilities in this frequency range and a survey speed at least 25
times as great.
⇒ 各SWGが、それぞれのテーマでこの要求について持ち帰って検討 	Baseline Designについて

2 各SWGからの報告
1.1 HI surveys and galaxy evolution
Level 1 science requirementsについての議論
Tom Oosterlooより
1: The Level 1 Science Requirements (the document I sent you afew days ago). The aim of the requirements document is not to"define" the surveys one would like to do with SKA1, but to give
context to the technical requirements. Nevertheless, I would feelmuch better if there is an explicit mention of the ambition towork on HI in emission out to large redshifts (i.e. beyond 800MHz) and to include a sensitivity requirement of a single
high-z pointing after 1000 hr. It is difficult to translate therequirements stated as they are now, into requirements for single
feed deep pointings. So if you agree, I will suggest to Robert toinclude such a thing.	

Level 1 science requirementsについての議論
5: Bands for SKA1-Mid. We should make up our minds what wewant to do here. The conclusion of the Jodrell meeting was adifferent definition of the bands so have cover high-z emission
better. In the mean time, Justin Jonas has made anotherproposal (band 1 = 350-650 MHz, band 2 600-1100 MHz andband 3 1-3 GHz). Band 1 and 2 would then be octave receivers
and would have good performance, band 3 would be 20-30%
worse. In our proposal band 1 would be the bad receiver. I havebrought Justin's proposal up before (because I like it) and someof you commented that Justin's proposal would make it
impossible do use deep integrations of nearby galaxies for high-zstudies. My question is: high feasible is it to use nearby galaxy
observations for this? 	

2.2 EoR and Dark Ages2.3 Cosmic magnetism
国際SKA宇宙磁場科学検討班：メンバー(20 + 2 SKAO staffs*)	
Takuya Akahori

Annalisa Bonafede	Ivan Agudo	

*Tyler Bourke	

Rainer Beck
Bryan Gaensler

Luigina Feretti

Marijke Haverkorn
George Heald*James Green	

Federica Govoni(co-chair)	

Melanie Johnston-Hollitt(co-chair)

Lisa Harvey-Smith
Larry Rudnick

Katia Ferriere

Tobia Carozzi

Keitaro Takahashi

Anna Scaife

Ann Mao	
Dominic Schnitzeler

Jeroen Stil

18	
Russ Taylor

国際SKA宇宙磁場科学検討班：
活動拠点	

CIBERSKA
http://www.cyberska.org/pg/groups/31244/ska1cosmic-magnetism-science/	

PBworks
http://skamagnetism.pbworks.com/w/page/65580311/FrontPage+ 定期的な電話会議 + メールベースでの議論+ 研究会の開催(2015年IAU総会中を計画中)	

19	

国際SKA宇宙磁場科学検討班：
Baseline Designへのインプット(1/2)
	• Cosmic Magnetism Science Drivers
1) The Galactic magnetic field
2) Magnetism and galaxy Evolution3) Mangetic fields in galaxy clusters4) Detection and Charaterization ofmagnetic fields in the cosmic web	Fletcher et al. (2011)

Vacca et al. (2010)

Oppermann et al. (2012)

Akahori & Ryu (2010)20	

国際SKA宇宙磁場科学検討班：
Baseline Designへのインプット(1/2)
	

••
•
•
•

Frequency: As wide frequency range as possible, not to have gaps in range
between the instruments. For SKA1-survey, if no PAF Band1, going to slightly
lower frequencies would be better for RM synthesis.
Angular Resolution: High angular resolution reduces beam depolarization
Largest Angular Scale: As minimum as possible (SKA1-low stations not largerthan 35 m).
Polarization Purity: Proper info. on polarization performances are missed in thedocument
Survey Speed: Apparent similarity in capabilities between SKA1-mid and SKA1survey. Higher survey speed for the one dedicated to wide field observations.21	

2.4 Pulsars for fundamental physics
Pulsar Science Working Group (PSWG)	
• 参加者： 今井 裕
– SKA-JP Astrometry sub-WG世話人– SKAでVLBI/astrometryを想定しているのが PSWG
(with Adam Deller)• SKA Assessment Workshop of PSWG (2013 July 17-18)– Design Reference Mission の見直し
– それぞれの天域における最適掃天周波数
銀河系中心>10 GHz (SKA-mid), 銀極方向 ~100 MHz(low)– パルサー探査の戦略• Low-band: 広い視野、乏しい角分解能• mid-band: 幾つbeamが必要？
• 1000個の程度のミリ秒パルサーが検出できるはず(SKA1)– データサイズ: dispersion measureの測定／除去VLBI in SKA	• Baseline Design ではVLBIに関しては殆ど言及なし
à新規追加要望項目に• Pulsar astrometry は重力波検出(PTA)においても重要– 理想的な点源à高感度ほど高精度(σ~20µas)– 年周視差： 短期間ではastrometryで、長期(>10年)ではpulsar timingの方が精度が高い– 位置・固有運動： astrometryでないと計測できない• In-beam (low) or multi-beam (mid) astrometry– L-band(1.6 GHz)で数10µasの年周視差計測精度(Deller+12)• SKA1 + existing telescopes– LBA (南半球), EVN (欧州), EAVN(東アジア)– 多数基線による大気遅延残差（水蒸気,電離層）の影響の緩和– 相関局との光ファイバー結合(>40 Gbps)