A Proposal for Constructing a New VLBI Array,‘Horizon Telescope’ Makoto Miyoshi & Seiji Kameno

1. A Proposal for Constructing a New VLBI Array,‘Horizon Telescope’ Makoto Miyoshi & Seiji Kameno NAOJ IVS2002, Tsukuba, Japan 2002.02.05

2. The existence of the black hole in the universe was confirmed in the last century.

3. example 1 : M87, Hubble Space Telescope, MBH=3.0×109M sun Hubble Space Telescope revealed the existence of massive black hole at the center of the M87.The HST measured the gas velocity around the central core of the M87 from Doppler effects, and found the mass of the core is about 3.0×109 Msun .

4. example 2 : NGC4258, VLBA, MBH=3.9×107M sun Using the VLBA, a high velocity Keplarian disk around the core was found. More than 1000km/sec at the radius of 0.13 pc means that the central mass exceeds 3.9 ×１０７Ｍsun. Only within the radius of 0.3 ly 3.9×107 solar mass exists、such a high density cannot be explained without black hole. Herrnstein et al 1999 Miyoshi et al 1995

5. example 3 : Our Galactic Center SgrA*, Ground NIR Telescopes, MBH=2.6×106M sun Stellar motion at the center of the Galaxy The motions are more than 1000km/sec. Genzel et al 1999 Ghez et al 2000 http://antwrp.gsfc.nasa.gov/apod/

6. example 3 : Our Galactic Center SgrA*, Ground NIR Telescopes, MBH=2.6×106M sun From orbital motion study of high velocity stars at 0.005pc from SgrA*, the central mass is determined to be 2.6×106M sun

7. From the dynamical measurements,no one can deny the existence of black hole in the universe today. But, No one has seen them.

8. ＶＬＢＡ（VLBIArray） ２５ｍ鏡１０台 最大８０００km基線 （最小フリンジ間隔 ０．２mas＠４３ＧＨｚ） ３００ＭＨｚ～４３ＧＨｚ With the highest resolution of VLBI, even the accretion disks can not be seen so far.

9. Radio Interferometer has been trying to resolve the central part of the monsters. This figures shows the struggles of people for decades.

10. The nucleus of M87(VLA,VLBA）This is one of the highest resolution VLBI maps. The true face of central massive black hole cannot be seen.

11. The accretion disk of a black hole. • related outer disks are now revealed in some case

12. NGC4261outer disk with d=800ly too big for relativisticaccretion disk

13. NGC4258 masing and rotating gas disk with r=0.27pc still big for relativistic accretion disk

14. The accretion disk of a black hole. • related outer disks now revealed in some case • But,the central black holes, their accretion disks can't be seen so far at all.

15. How is the appearance of Black hole? Black hole alone can not be seen. But, black holewith some emitter can be seen. Several theorists have investigated the appearances of such black holes.

16. A simulation of the appearance of black hole with accretion disk (Fukue et al 1989). Light from the other side is bended by the black hole gravity, and then we can see opposite side. At the center ‘black hole ‘ can be seen from where no light come towards us.http://quasar.cc.osaka-kyoiku.ac.jp/~fukue/

17. The most promising candidate for observing black hole is the Galactic Center SgrA*. The reason is that.... Its angular size is the largest in the universe.

19. VLBI images of the SgrA* from 5GHz to 43GHz. from Ｌｏ　ｅｔ　ａｌ　（１９９９） At Lower Frequencies from 5 GHz to 43 GHz, the image of true Black hole and its accretion disk of SgrA* was blurred by plasma surrounding the core. Then what shall we do?

20. At sub millimeter observations, the effect of the scattering is reduced sufficiently, then we can observe the black hole of SgrA*

21. 510GHz no scattering 10Rs,30μas The appearance of Sgr A * at sub millimeter observations Takahashi & Mineshige (2002)

22. What is the meaning of the detection of such figure ? The test of relativity at strong gravity (Nobel Prize level) The birth of ‘Observational Astronomy of Black Hole Accretion Disk’

23. The Black Hole Event Horizon Telescopefor SgrA* observations 3 options at now

24. SMA in Hawaii PLAN No.1 put sub-millimeter telescopes at high land in Australia and New Zealand, collaborated with the SMA and the ALMA occasionally to get improved images. ALMA in Chili Southern Hemisphere sub-mm VLBI array.

25. PLAN NO.2 Go Southwards Further ! The Antarctic is another good cite for sub-mm observations like ALMA Chili cite. The Antarctic Continent sub-mm VLBI array.

26. PLAN NO.3 Go to Outer Space ! No atmospheric absorption, No need for atmospheric phase compensation. Best cite. But much expensive, complicated system Space to space, sub-mm wave VLBI array.

27. Horizon Telescope for monitoring the black hole at SgrA* Obs. Frequency : to escape from the scattering effect of circum nuclear plasma Obs. Site : to receive sub-mm radio emission from low declination object ３５０～８００ＧHz sub millimeter wave length 1) Space, 2) Southern Hemisphere highlands or the Antarctic Stations： to get sufficient uv coverage for high dynamic range in image More than 10 like VLBA Array Size: to attain less than 10micro arc seconds resolutions More than 8000 km (at 500 GHz)

28. Problem 1 Technique ? OK! with the technology of the ALMA construction. ALMA conceptual image courtesy of the European Southern Observatory (ESO

29. Problem 2 Money ? No Money at Present in Japan I'm Junichiro Koizumi.I have dedicated myself to introducing structural reforms. I am convinced that economic growth cannot be achieved without them. Budget is expected after the ALMA construction and the structural reforms.

30. Problem 3 powerful blood ? At least Two in Japan Need another 5 for seven samurai

31. This is the goal where VLBI astronomy must reach. Thanks From Fukue et al