1. sub-mm VLBI for resolving super-massive black hole Mareki Honma VERA / Mizusawa VLBI observatory, NAOJ

2. Target : touching the event horizons of BHs Fukue et al 1989 AGN core is most-likely a super-massive black hole. Yet, there is no confirmation of existence of event horizon Direct detection of BH shadow is an ultimate confirmation of existence of BH. (or negative results may indicate an existence of naked singularity !?) New breakthrough for experimental BH physics!?

3. BH size sourceM BH /M sun Distance Angular radius Sgr A*4 x 10^68 kpc10μas M873 ~ 6 x 10^915 Mpc4 ~ 7μas M1041 x 10^910 Mpc2μas Cen A5 x 10^74 Mpc0.25μas Shadow diameter : 1~5 times Schwartshild radius For imaging shadow, ~ 10μas resolution is required

4. Angular resolution of telescopes Wavelength – angular resolution diagram VSOP-2 VLBA VERA ALMA AKARI SUBARU HST cm wave IR opticalmm wave VLBI Connected array Single dish Resolution in mas λ 1 mas 1 arcsec Submm VLBI Sgr A* BH size

5. Doeleman+(2008) ･ 37±(16,10) Intrinsic diameter of Sgr A* ･ Non detection on the JCMT-CARMA （ 3075 km ） ARO/SMT － CARMA(600km) ARO/SMT － JCMT Non-imaging analysis (traditional UV distance plot) 230GHz VLBI with JCMT – SMTO – CARMA

6. Sub-mm VLBI of Sgr A* 1995 MarIRAM30m-PdBKrichbaum+ (1998) … 2006 MarHawaii-SMTO-CARMAfailed 2007 MarJCMT-SMTO-CARMADoeleman+(2008) but IRAM/PdB failed 2009 MarHawaii-SMTO-CARMA SMA phase-upFish+(2011) 2010 MarHawaii-SMTO-ASTE 2011 MarHawaii-SMTO-CARMA-APEX-IRAM but not fringes from Chile and Europe …

7. Sub-mm VLBI with ASTE (2010) Chilean station will be a key for Sgr A* observations good site & longest baselines JCMT CARMA ASTE SMTO UV coverage for Sgr A* （ red: UV with ASTE ） fringe spacing ~30μas

8. Sub-mm VLBI in 2011 Mar/Apr International campaign from Mar. 28 to Apr. 5 Hawaii CARMA SMTO (APEX) (Pico Veleta) Planned Array for April 2011 obs. US array (Hawaii-CARMA-SMTO) is the core European stations may join (APEX / IRAM 30m)

9. Steps toward future Re-trial with Chilean stations (ASTE/APEX) ? Green land (ASIAA) : ALMA prototype move in 2013 ? LMT : VLBI capability ? ALMA phase-up is the key (both sensitivity & imaging capability) Proposal to NSF MRI in 2011 Haystack/ NRAO/ MPI/ NAOJ/ ASIAA etc. Highly-ranked by NSF review and will be funded this year. observation from ~2015 (?) Large (sub-)mm telescope will be very useful.

10. ALMA phase-up plan Phased-sum in baseline correlator data transfer to OSF & recording there Japan’s part : optical-fiber transmission between ALMA – OSF OSF(@2900m) Optical fiber (8 x 8Gbps) Correlator (sum-up)

11. Science cases BH shadows : Sgr A* & M87 Jet monitor: launch/accelaration mechanism Detailed structure of accretion disk Time variation (Sgr A*: 15min, M87 : a few days) of structure near BH Rotation of hot spot/disk patch > test of General Relativity in strong gravity field. + non-BH sciences SFR/AGB masers, astrometry (LMC/SMC, for instance) M87 at 43G BH simulation Gammie & Noble New laboratory for “Black Hole Physics”

12. Discriminating models for M87 Simple simulations how ALMA works out Ring between 15.0 - 25.5μas Gaussian with 13.0-μas- radius shadow Gaussian with 38μas FWHM Disk with 30μas radius Chile baselines Simulated and observed visibilities vs. UV distance Chile baselines

13. γ-ray emitting AGNs Example : 3C84, radio jet detection (VERA) after γ-ray flare (Fermi) Radio light curve VLBI map (2 x 2 pc), at 22 GHz Nagai+(2010) cm + (sub-)mm VLBI will lead comprehensive understanding (higher resolution & lower optical depth …) SSC model for Mrk 501 (Kino+2001) γ-ray mitting region:<1000 AU

14. Science cases around 2020 Basic assumption : BH shadow itself is already seen Jet monitor: launch/accelaration mechanism Detailed structure of accretion disk Time variation (Sgr A*: 15min, M87 : a few days) of structure near BH Rotation of hot spot/disk patch > test of General Relativity in strong gravity field. M87 at 43G BH simulation Gammie & Noble New laboratory for “Black Hole Physics”

15. role of new large telescope in Chile in VLBI Even if ALMA phase-up goes, machine time should be very limited (machine time is very important, e.g., for monitor). 50m(?) in Chile will expand possibility of doing VLBI. Combination of 50m in Chile and phase-up ALMA (50 of 12- m) equivalent to 98-m dish !! 50m-ALMA for short baseline obs. (30 km – 100 km?) Providing new “longest” baseline for ALMA > additional science cases, such as resolving nearby giant stars

16. Summary Sub-mm VLBI will open up wonderful science cases with ultra-high resolution: resolving BH shadows, Jet launching / gamma- ray-jet connection and more… Large (sub-)mm telescope will be useful to expand science cases with sub-mm VLBI (e.g., monitor etc.)