An idea of Space mm/sub-mm VLBI Array

Xiao-Yu Hong ( 洪晓瑜 )J un-Hui Zhao ( 赵军辉 )Zhi-qiang Shen ( 沈志强 )

Shanghai Astronomical Observatory

( 中国科学院上海天文台 )

1. VLBI in China2. VLBI in the world3. Scientific requirement for Higher

resolution 4. VLBI in future5. How to find the DIRECT evidence of

BH?6. An idea of Space mm/sub-mm VLBI

Array

Outline

1. VLBI in China

Seshan radio telescope

Shanghai Correlator

Nanshan radio telescope

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

VLBA

VSOP

Australian LBA & APT

VERA

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…

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).

B B

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; SMA located 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:

B

mas 5.1 km 10000 cm; 6 BGround-based VLBI:

mas 5.0 km 30000 cm; 6 BVSOP:

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?Zooming in on Black Holes

•

• Candidate Objects? • Which observed frequencies?• In radio bands: facilities?

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

5.1 Candidate Objects?

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!