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VERA ー 最新の成果と今後の展望 ー Mareki Honma Mizusawa VLBI observatory, NAOJ Galaxy-scale maser astrometry Sun Galaxy’s center Parallax Galaxy Center D= 8 kpc π= 125 μas Galaxy scale astrometry requires 10μas accuracy Galaxy scale astrometry = frontier in 21st century (c.f., astrometric missions like SIM, GAIA, JASMINE) VERA : VLBI Exploration of Radio Astrometry Construction completed in 2002 Regular observations from 2004 Mizusawa Iriki Ishigaki-jima Ogasawara Target sources : Galactic masers (H2O@22GHz, SiO@43GHz) New aspect: dual-beam for phase-referencing 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 telescope dual-beam receivers Phase-referencing Target source reference Dual-beam platform (2.2 deg max) atmosphere VERA station Dual-beam phase compensation ~1 mas W49N and OH43.8-0.1 again (on 23/Jul/2002) Phase residual : ~8 degree in RMS Current status of astrometry with VERA Location of maser sources for which parallax/proper motions are obtained Schematic view of Galaxy Solar neighborhood NGC 281 ON1 G34 L1204 SY Scl R UMa G14 WB755 NGC 1333 ρ oph Orion S Crt I06058 T Lep VY CMa W49N I19213 OH43 AFGL2789 I19181 WB621 NGC 281 ON2 Sgr A S269 Sun Illustration courtesy: NASA/JPL-Caltech/R. Hurt (SSC/Caltech) Parallax + proper motion Proper motion 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 Galaxy Center S269 Sun Honma et al. (2007) Flat rotation curve out to 13 kpc, plenty of dark matter 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) ON 1 • ON1 has both H2O and Methanol masers H2O maser parallax 2.4 +/- 0.1 kpc (Nagayama+ in prep) Maser locations c.f. ) Methanol maser parallax 2.57+0.34-0.27 kpc by EVN (Rygl+ 2009) IRAS19181 • D = 5.26 +/- 0.42 kpc (Nagayama + in prep.) • Close to W51M (~5.1 kpc), though kinematic distances differ (due to V_LSR difference) Nearby SFRs • 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) Dame et al.1987 G14.33-0.64 & Sgr Arm • D = 1.12 +/- 0.13 kpc (Sato et al. 2010) Sun G14 Local arm and Sgr arm traced with masers Combined analysis of VLBA/VERA • 18 sources published by 2008 10 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 : 0.651 +/- 0.133 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 Orion distance measurements • 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) Source I • 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) Position of radio sources (Menten et al. 2007) Trapezium can be observed with Nano-JASMINE ? AGB star S Crt • 年周視差 2.33±0.3 mas (VERA) HIPPARCOS Pi = 1.27 mas err 0.92 mu_a -3.37 mas/yr err 1.00 mu_d -4.67 mas/yr err 0.75 Nakagawa et al. (2008) 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 = -3.62 LogP +1.57 (Nakagawa et al. in prep) Good luck for Nano-JASMINE !