An idea of Space mm/sub-mm VLBI Array

An idea of Space mm/sub-mm VLBI Array Xiao-Yu Hong (洪晓瑜) Jun-Hui Zhao (赵军辉) Zhi-qiang Shen (沈志强) Shanghai Astronomical Observatory (中国科学院上海天文台)

Outline • VLBI in China • VLBI in the world • Scientific requirement for Higher resolution • VLBI in future • How to find the DIRECT evidence of BH? • An idea of Space mm/sub-mm VLBI Array

Nanshan radio telescope 1. VLBI in China Seshan radio telescope Shanghai Correlator

Regular VLBI observations of Sheshan and Nanshan telescopes • EVN (European VLBI network) • IVS (International VLBI service for Geodesy and astrometry) • APSG (Asia - pacific space geodynamics project ) • VSOP (Shanghai telescope joint VSOP survey program) • Some other ad hc VLBI observation

2.VLBI Facilities around the world The Global mm-VLBI Array

3. Scientific requirement for Higher resolution • Radio jet & Black hole physics • Radio source evolution • Astrometry • Galactic and extra-galactic Masers • Gravitational Lenses • SNR and GRB studies • Nearby and distant starburst galaxies • Nature of faint radio source population • HI absorption studies in AGN…

B 4.VLBI in future • VLBI contributes the highest resolution in modern Astronomy • The very high angular resolution of VLBI can be increased further in two ways: either by using longer baselines (to space) or by observing at shorter wavelengths (mm and sub-mm wavelength).

4.1 The Global mm-VLBI Array

mm-VLBI is now able to provide good quality images in the 3mm band, with an angular resolution of typically 50-70 micro-arcseconds. • At shorter wavelengths the VLBI technique is still in its development stage [although first detections were recently made at 2mm (129, 147 GHz) and at 1.3mm (215 and 230 GHz)]. • an angular resolution which is unsurpassed by any other present astronomical imaging method.

4.2 SMA • SMA: 8 X 6米; • Baseline: 8mto 508m; • SMAlocated at Mauna kea; • Frequencies:180GHz to 900GHz.

4.3 ALMA 64 X 12 m Longest baseline:14 kilometers Frequencies: 70 to 900 GHz. ALMA will be the most powerful sub-mm array on the ground in next 30 years

4.4 Space VLBI • VSOP • ARISE • RadioAstron • VSOP2 • Space VLBI Array?

Angular resolution: Ground-based VLBI: VSOP: VLBI beyond the Earth diameter: VSOP mission ISAS, Japan + world-wide collaboration (in orbit since 1997)

Advance Radio Interferometry between Space and Earth

RadioAstron

VSOP-2 (Japan)

5. How to find the DIRECT evidence of BH? • Candidate Objects? • Which observed frequencies? • In radio bands: facilities?

5.1 Candidate Objects? What is the most possible of 10 candidates? NGC 4258? MGC 4261? M87? 3C273? 3C345? 3C279? 1156+295? 0954+556?First 20? First 50?

5.2 Which frequencies: • Gamma ray? • X-ray? • UV? • Optical? • Infrared? • Radio? Sub-mm? mm? cm?

5.3 Radio: facilities • Single Disk? • SMA? • ALMA? • VLBI: VLBA? EVN? The Global mm VLBI Array? VSOP? VSOP-2 Space mm/sub-mm VLBI array?

5.4 Space mm/sub-mm VLBI Array(SMVA)? • Sensitivity request? • Distance of baseline request? • Frequencies request? > 100 GHz to TGHz? • (u,v) coverages?

6. An idea of Space mm/sub-mm VLBI Array Antennas: • 5 or 6 antennas with diameters in 2 meters • No puckering is need -> good for high frequencies • One rocket with all the satellites • Sensitivity request? • Lower cost to current VSOP ideas

Orbit design: • Obtaining good (u,v) coverages • Distance of baseline request Orbit measure: • GPS, • Laser, • Ground VLBI Maser?

谢谢！Thank you!

An idea of Space mm/sub-mm VLBI Array