VERA ー 最新の成果と今後の展望 ー Mareki Honma Mizusawa VLBI observatory, NAOJ

Galaxy-scale maser 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

VERA : VLBI Exploration of Radio Astrometry Ishigaki-jimaOgasawara Iriki Mizusawa Target sources : Galactic masers New aspect: dual-beam for phase-referencing Construction completed in 2002 Regular observations from 2004

Astrometric missions Satellite mission for Galaxy-scale astrometry GAIA (ESA) 2012 SIM (NASA) 2015? JASMINE (JAXA) 2018? Target accuracy is ~10 μas, the same with VERA

Dual-beam receiving system dual-beam receivers VERA station reference atmosphere Target source telescope Dual-beam platform (2.2 deg max) Phase-referencing

Dual-beam phase compensation W49N and OH again (on 23/Jul/2002) Phase residual : ~8 degree in RMS ~1 mas

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 ON1 WB755 WB621 G34 I19181

S 269 proper motion S269 motion with respect to LSR : (V_l, V_b) = (-4.6, -4.1) km/s >> similar galactic rotation velocity at the Sun and at S269 S269 Sun Galaxy Center Flat rotation curve out to 13 kpc, plenty of dark matter Honma et al. (2007)

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

ON1 ON1 has both H2O and Methanol masers Maser locations H2O maser parallax 2.4 +/- 0.1 kpc (Nagayama+ in prep) c.f. ) Methanol maser parallax kpc by EVN (Rygl+ 2009)

IRAS19181 D = / kpc (Nagayama + in prep.) Close to W51M (~5.1 kpc), though kinematic distances differ (due to V_LSR difference)

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) Comparison of Cepheus distances Cep-A (700+/-40 pc, Moscadelli+, VLBA) L1204(764+/-27 pc, Hirota+, VERA) L1206 (775+/-90 pc, Rygl+, EVN)

G & Sgr Arm D = / kpc (Sato et al. 2010) G14 Sun Local arm and Sgr arm traced with masers

Combined analysis of VLBA/VERA 18 sources published by VLBA Methanol 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

Summary of current status and future VERA Kpc-scale astrometry is already achieved with VERA Parallaxes and proper motions are obtained for ~20 sources ~70 sources have been observed, still to be analyzed ~1000 sources within next 15 years VLBA large project (Reid, Menten, Brunthaler +) will also observe ~500 sources. Main targets should be disk sources in the northern hemisphere > The bulge will remain to be explored with JASMINE !?

On-going up-grades of VERA New bands (6.7GHz) : more sources Array expansion : higher sensitivity, longer baselines (=> better accuracy) Wide-band recording : higher sensitivity (=> better accuracy)

6.7GHz receiver for VERA Developed by Osaka-pref. Univ. (Ogawa lab.) Installation finished in May 2009 (all stations) T_rx ~ 60 K Tsys ~ 120 K efficiency ~50%

Preliminary results : W3(OH) Parallax : / mas (Matsumoto et al. in prep) c.f., pi = 0.512±0.010mas (Xu et al.2006)

Collaborations with East Asian VLBI stations KVN participation provides shorter and denser UV > better image China participation expands east-west baseline > better astrometry

Collaboration with nano-JASMINE Calibration VERA can provide calibration stars for which parallax and proper motions are already obtained. position comparison / link of radio and IR frame, + down-link with Mizusawa 10m

GMR-A (VLBA 15 GHz) /-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 Trapezium can be observed with Nano-JASMINE ?

AGB star S Crt 年周視差 2.33±0.3 mas (VERA) Nakagawa et al. (2008) HIPPARCOS Pi = 1.27 mas err 0.92 mu_a mas/yr err 1.00 mu_d mas/yr err 0.75

Period-Luminosity Relation of Mira VERA observations of SY Scl, T Lep, R UMa, S Crt (SR) are used to precisely calibrate the P-L relation of Mira Mk = LogP （ Nakagawa et al. in prep ）

Good luck for Nano-JASMINE !