1. Galactic Structure seen with VLBI astrometry Mareki Honma Mizusawa VLBI observatory, NAOJ 21/Jul/2009 @ Astrometry workshop in Socorro

2. Science with VLBI astrometry VLBI astrometry : Powerful tools in various field Galaxy structure => this talk SFRs=> talk by Loinard Pulsars=> talk by Chatterjee Stars=> talk by Torres, Peterson, Choi Extra-Galaxies=> talk by Brunthaler Planet search=> talk by Bower Reference system (ICRF) => talk by Charlot, Jacobs General relativity test => talk by Fomalont (?) growing up rapidly (c.f. less than 1 day for astrometric contributions in VLBA 10 th anniversary symposium in 2003)

3. Galaxy-scale astrometry Galaxy’s centerD= 8 kpc π= 125 μas Galaxy scale astrometry requires 10μas accuracy Galaxy scale astrometry = frontier in 21 st century (c.f., astrometric missions like SIM, GAIA, JASMINE) Sun Galaxy Center Parallax

4. Optical astrometric missions Satellite mission for Galaxy-scale astrometry GAIA (ESA) 2012 SIM (NASA) 2015? JASMINE (JAXA) 2017? Target accuracy is ~10 μas

5. VLBI astrometry Beam size of VLBI ~ 1 mas or better 10 μas accuracy ~1/100 of beam 10 μas is doable if good phase calibration can be done phase referencing to cancel out the troposphere effect VLBI station reference atmosphere Target source Phase-referencing VLBI

6. VERA : VLBI Exploration of Radio Astrometry Ishigaki-jimaOgasawara Iriki Mizusawa Target sources : Galactic masers (H2O@22GHz, SiO@43GHz) New aspect: dual-beam for phase-referencing Construction completed in 2002 Regular observations from 2004

7. Current status of astrometry with VERA Location of maser sources for which parallax/proper motions are obtained Sun S269 Schematic view of Galaxy Illustration courtesy: NASA/JPL-Caltech/R. Hurt (SSC/Caltech) NGC 281 ρ oph S Crt Orion NGC 1333 Solar neighborhood VY CMa Parallax + proper motion Proper motion Sgr A OH43 W49N ON2 T Lep SY Scl R UMa L1204 I06058 AFGL2789 I19213 G14

8. Distance to Orion KL Astrometry of H2O masers in Orion KL Hirota et al. (2007) D = 437 +/- 19 pc pi = 2.29 +/- 0.1 mas Orion nebula with Subaru

9. GMR-A (VLBA 15 GHz) 389 +24/-21 pc (Sandstrom et al. 2007) GMR A/F/G/12 (VLBA 8GHz) 414+/-7 pc (Menten et al. 2007) H2O maser in Orion KL (VERA) 437+/-19 pc (Hirota et al. 2007) SiO masers in source I (VERA) 419+/-6 pc (Kim et al. 2008) Orion distance measurements Position of radio sources (Menten et al. 2007) Source I

10. Nearby SFRs Dame et al. 1987 Astrometry of SFRs within ~1 kpc from the Sun –Orion-Monoceros (Orion KL: Hirota+2007, Kim+2008) –Perseus (NGC1333: Hirota+2008)) –Ophiuchus (rho-oph: Imai+2008) –Cepheus (L1204, Hirota+2009) –VY CMa (Choi+2009) –Orion, Taurus, Cepheus, Ophiucus (WTTS: Menten+, Torres+, Loinard+) see Talk by Loinard

11. NGC 281 & Galactic Super bubble NGC 281: Star-forming region on a super bubble H2O maser located in NGC 281 west Motions away from the Galactic plane (Sato et al. 2007) energy : 3 x 10^52 erg (multiple SNe) age : ~ 10 Myr ~20 km/s 10 deg Galactic Longitude 300 pc HII region HD500 5

12. Super bubble structure Both NGC 281 and IRAS00420 are associated with the supper bubble, but separated by 20 km/s in radial velocity Distance to IRAS00420 was measured with VLBA (2.2 kpc) Moellenbrock et al. Two sources are located on the different sides of the 3D-Bubble ?

13. S269 and Galactic Rotation Parallax and proper motions of S269 provides a strong constraint on outer rotation curve Consistent with flat rotation curve out to 13 kpc No dark matter S269 D ： 5.28 +/- 0.24 kpc Honma et al.(2007)

14. RC from 7 – 13 kpc Oh et al. (2009) obtained distances for three more sources IRAS19213+1723 AFGL2789 IRAS06058+2138 D= 2 ~ 4 kpc Basically cosistent with FRC (but slightly slow rotation for Perseus arm sources)

15. VLBA

16. Reid & Brunthaler (2004) 8 year monitor of Sgr A* Accurate measurement of Ω0 = Θ0/R0 (29.45+/-0.1 km/s/kpc) Sgr A* against J1745-283 Sgr A* motion

17. VLBA maser astrometry OH (AGB) CH3OH, H2O (SFR) Vlemmings et al.(2007) Xu et al. (2007) W3

18. 12 GHz Maser Parallaxes Current parallax results More in progress CfA : Reid MPIfR: Menten, Brunthaler Arcetri: Moscadelli Nanjing: Xu, Zheng et al.

19. Combined analysis of VLBA/VERA 18 sources published by 2008 10 VLBA Mehtanol maser project (Reid+) 4 VERA H2O maser 4 others from VLBA Pitch angle of Perseus arm 16 +/- 3 deg four arm spiral ? Galactic constants R0 = 8.4 +/- 0.6 kpc Θ0=254 km/s +/- 16 km/s (Ω0=30.3 +/- 0.9 km/s/kpc) Reid+ 2009

20. Slow rotation of HMSFR HMSFR appear to rotate slowly Residual against flat rotation curve with R0=8.5 kpc, Θ0=220 km/s Comparison with Hipparcos UVW results

21. Maser Astrometry with other array 6.7GHz Methanol maser astromery with EVN: successfully detected parallaxes for some sources (Rygl, Brunthaler et al.) 6.7G observations also on-going with LBA in Australia 6.7 GHz methanol will be useful probe (plenty of sources, bright, stable many stations … ) Rygl+2008, with EVN

22. Summary of current status VERA ~12 sources with measured parallax ~ 80 H2O/SiO sources done, ~1000 in next 15 years, new 6.7G receiver (methanol) VLBA H2O, CH3OH (12G) astrometry ~ 20 sources plan for Galaxy astrometry as large program plan for CH3OH maser receiver (6.7G) EVN some initial results from 6.7GHz methanol maser astrometry Australia Tasmania-U group is interested in 6.7G maser astrometry international collaborations will be beneficial for all

23. Future prospect Toward better understanding of MWG More sources new bands : e.g., new 6.7G receiver plan for VERA/VLBA Better accuracy –Better calibration (troposphere/ionosphere) new technique –Wider bandwidth (=> nearer but fainter calibrator) new recorder (4Gbps for VLBA, 8Gbps for VERA) –Longer baselines international collaborations

24. future collaborations What we are doing are : VERA+EVN joint 6.7G obs. (since 2009) VERA+LBA test obs. at 6.7G (2009 May) VERA/EAVN at 6.7G (plan in 2010 ?) More in futures … VERA/EVN/VLBA joint obs. ? VSOP-2 + ground VLBI astrometry ? source sharing ? and more …