1. The East-Asian VLBI Network: Synergy between FAST and EAVN W AJIMA, Kiyoaki ( 輪島 清昭, KASI) (on behalf of the EAVN Tiger Team) 2015 年 7 月 31 日 FAST 早期科学国际研讨会 Overview of EAVN Expected Specifications, Current Activities Results of Fringe Test Observations Collaboration between FAST and EAVN Summary Contents

2. In 2005, ‘East Asian Core Observatories Association (EACOA) was established and several WGs were arranged under EACOA, one of which is ‘East Asian VLBI Consortium’. A small task force, ‘the EAVN Tiger Team’ was organized on June 2013 to handle various issues related to EAVN. The East-Asian VLBI Network (EAVN) 2/13 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary – To promote VLBI test observations – To proceed data reduction of test observations – To clarify the problems for future regular operation and open-use A group photo of the EAVN Tiger Team Meeting held on 29 July 2014 at Shanghai Astronomical Observatory.

3. The EAVN Tiger Team 3/13 China (7) – SHAO (Shanghai): Tao A N ( 安涛 ), Willem A. B AAN, Wu J IANG ( 江 悟 ), Bo X IA ( 夏博 ) – XAO (Ürümqi, Xinjiang): Ming Z HANG ( 张明 ) – YAO (Kunming, Yunnan): Longfei H AO ( 郝龙飞 ), Min W ANG ( 汪敏 ) Japan (5) – NAOJ: Noriyuki K AWAGUCHI ( 川口則幸 ), Hideyuki K OBAYASHI ( 小 林秀行 ), Yuanwei W U ( 吴元伟 ) – Toyo University: Yoshiaki H AGIWARA ( 萩原喜昭 ) – Yamaguchi University: Kenta F UJISAWA ( 藤澤健太 ) Korea (5) – KASI: Taehyun J UNG ( 鄭太現 ), Jongsoo K IM ( 金鍾秀 ), Se-Jin O H ( 吳世珍 ), Duk-Gyoo R OH ( 盧德圭 ), Kiyoaki W AJIMA ( 輪島清昭, Chair) 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary

4. EAVN: Specifications Number of (potential) telescopes: 21 – Korea: 4, China: 5, Japan: 12 (Possible) frequency coverage: – 6.7 GHz (12 stations), 8 GHz (16), 22 GHz (18), 43 GHz (10) – (2, 86, 129 GHz) Minimum sensitivity for 7-σ fringe detection (assuming τ = 60 s) – 7 mJy (8 GHz), 30 mJy (22 GHz) (Expected) angular resolution: – 1.5 mas (8 GHz; Ogasawara – Nanshan (Urumqi)) – 0.6 mas (22 GHz; Ogasawara – Nanshan) – 0.7 mas (43 GHz; Ogasawara – Tianma (Shanghai)) (Expected) recording rate: ≧ 1 Gbps (= 256 MHz BW) (Currently-used) correlator: – KJCC (Korea): KJJVC and DiFX – SHAO (China): DiFX

5. Examples of (u, v) Coverage EAVN ‘full’ array at 8 GHz for a source with δ = +60 deg – 10-hour duration Expected (u, v) coverage and synthesized beam of an EAVN ‘full’ observation at 8 GHz. 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary

6. EAVN: Test Observations 6/13 Fringe test status – 8 times to date: 2013 (2), 2014 (5), 2015 (1) – Stations participated in: 4 (2014 Sep) – 11 (2013 Sep), 16 stations in total (CN: 4, KR: 4, JP: 8) – Observing frequency: 8 and 22 GHz – Observing mode: 256 MHz bandwidth (16 MHz×16 ch), sampling rate of 1 Gbps – Polarization: RHCP (8 GHz), LHCP (22 GHz) – Correlator: KJJVC at KASI, and DiFX at KASI/SHAO 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary

7. 31 July 2015 FAST 国际研讨会 Results of Fringe Tests 7/13 8th fringe test on 2015 February 12 at 8 GHz – Source: 3C 454.3 – Correlator: KJJVC – Integration time: 1 min Ulsan – Tsukuba Ulsan – Kunming Tsukuba – Kunming Ulsan – Shanghai Tsukuba – Shanghai Kunming – Shanghai We can obtain high fringe signal-to-noise ratio with small scattering in the fringe phase. The EAVN Specification Fringe Tests Collaboration Summary

8. 31 July 2015 FAST 国际研讨会 Results of Fringe Tests 16/20 7th fringe test on 2014 November 11 at 22 GHz – Fringes were detected for all baselines (source: W49N) – Comparison of correlation results (left: SHAO DiFX, right: KJJVC) The EAVN Specification Fringe Tests Collaboration Summary

9. Proposed Timeline 9/13 Year2014201520162017 Actions ・ 5-time fringe tests done ・ FTP data transfer test ・ Further fringe tests ・ Imaging tests, performance evaluation ・ Imaging tests ・ Science commissioning observations ・ Fringe tests at 43 GHz ・ (Early or late 2017) Risk-shared open-use at 6.7/8/22 GHz ・ Performance evaluation at 43 GHz Frequency8, 22 GHz6.7, 8, 22 GHz6.7, 8, 22, 43 GHz Purposes ・ Fringe detection from some telescopes in EAVN ・ Evaluation of array performance and imaging capability ・ Evaluation of array performance and array operation commissioning ・ Performance evaluation at 43 GHz ・ Initial scientific outputs from EAVN ・ Confirmation of performance at 43 GHz 31 July 2015 FAST 国际研讨会

10. Synergy between FAST and EAVN 10/13 Expected sensitivity at 2 and 8 GHz with FAST and EAVN (assuming A = 300 [m], η = 20[%], T sys = 25 [K]) – Minimum sensitivity for fringe detection with the integration time (τ) of 60 seconds  S_(min,fringe) = 1.0 mJy (7-sigma) – Expected rms image noise with τ = 8 hours  S_(min,image) = 0.15 mJy (7-sigma) 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary Low-luminosity AGNs (detection, morphology, AGN evolution, etc.) Star-forming region (6.7 GHz CH 3 OH with EAVN/1.6 GHz OH with FAST)

11. EAVN Observations at 6.7 GHz 11/13 VLBI monitoring of 36 methanol maser sources with EAVN at 6.7 GHz (Fujisawa et al. 2014, PASJ, 66, 31) – Telescopes participated in: VERA, JVN (Hitachi, Usuda, Yamaguchi), Sheshan – Spatial distribution of methanol masers with ~ 100 mas-scale has been obtained for 35 sources. Total/cross-power spectra (top left) and spatial distribution of 6.7 GHz methanol masers in a massive star- forming region 000.54–00.85. (Fujisawa et al. 2014) 10 April 2015 전파천문세미나 The EAVN Specification Fringe Tests Collaboration Summary

12. Examples of (u, v) Coverage FAST+EAVN ‘full’ array at 8 GHz for a source with δ = +30 deg (time duration of 8 hours) Expected (u, v) coverage of an EAVN ‘full’ array including FAST at 8 GHz. 31 July 2015 FAST 国际研讨会 – CVN, including FAST, are KEY telescopes for high-sensitivity VLBI observations with EAVN The EAVN Specification Fringe Tests Collaboration Summary 12/13

13. Summary 13/13 The EAVN Tiger Team has been organized and is carrying out various tasks to evaluate performance and to clarify the problems for future regular operation and open-use. In 2015, we will continuously carry out test observations to evaluate array performance and to check imaging capability. FAST will be a powerful telescope for not only single-dish observations but also VLBI observations. 31 July 2015 FAST 国际研讨会 The EAVN Specification Fringe Tests Collaboration Summary

15. 31 July 2015 FAST 国际研讨会 22 GHz 10-hour duration ‘Full’ array Examples of (u, v) Coverage δ = +60 degδ = +30 deg δ = 0 degδ = –29 deg

16. 31 July 2015 FAST 国际研讨会 Examples of (u, v) Coverage EAVN ‘full’ array at 22 GHz for a source with δ = +60 deg – 30-minute duration (snapshot) Expected (u, v) coverage and synthesized beam of an EAVN ‘snapshot’ observation at 8 GHz. Visibility coverage with respect to (u, v) distance for an EAVN ‘snapshot’ observation at 22 GHz.

17. Current Activities of the EAVN Tiger Team Execution of fringe tests – Eight-time fringe tests at 8/22 GHz Correlation and data analyses for performance evaluation – Comparison of correlation results between SHAO DiFX/KJJVC Thrashing out existing problems for future EAVN open-use Tiger team regular meeting (once or twice per month; via Skype) Face-to-face meeting (once per year; 1st face-to-face meeting was held on 2014 July 29 at SHAO) 31 July 2015 FAST 国际研讨会

18. EAVN: Test Observations #DateFrequencyAntennaSource 822KVN+VERAJVNCVN YSULTNSJMZIROGISYMTHHITKSHTMURKM 12013 Sep 24 ■ ●●●●●●●●●●● ■ ●●●●●●●●● 22013 Nov 22 32014 Jan 28 ■ ●●●●● ▲ ●● ■ ●●● ▲▲▲▲ ●●● 42014 May 27 ■ ●●●●●●●●●0528+134, DA 193 ■ ●●●●●●●●●● 52014 Sep 16 ■ ●●●●3C 273, W3OH 62014 Oct 18 ■ ●●●●●●3C 273, W49N 72014 Nov 11 ■ ●●●●●●●●3C 345, W49N 82015 Feb 12 ■ ● ▲ ●●●BL Lac, 3C 454.3 31 July 2015 FAST 国际研讨会

19. Observation and Data Flow JVN OCTADISK KVN Mark 5B CVN Mark 5B VERA OCTADISK KJCC (KJJVC/DiFX) SHAO (DiFX) Disk Pack/ 1-min FTP Mitaka Correlator Data transfer via optical fiber Specialized VEX Standard VEX DRG Digital BBC 31 July 2015 FAST 国际研讨会

20. Problems to be Solved Different bit assignment between CVN and KVN/JVN VEX file format of VERA, which differs from CVN/KVN Preparing a web-based interface to upload station logs, T sys files, and operator reports – Sharing the current web-based system of KaVA to avoid duplication of effort for development, and to consider convenience for operators Media shipping time from China, Japan to KJCC – FTP data transfer 31 July 2015 FAST 国际研讨会

21. Main Action Items for Future Open-Use Further fringe tests and imaging tests – Performance evaluation of the array Scheduling issues Preparation of web-based observation feedback to upload station logs, T sys files, and operator reports – Sharing the current web-based system of KaVA to avoid duplication of effort for development, and to consider convenience for operators Study of possible science cases – Extension of the current KaVA activity to EAVN? 31 July 2015 FAST 国际研讨会