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 center D= 　 8 kpc　　 π= 　 125 μas

Galaxy scale astrometry requires 10μas accuracyGalaxy scale astrometry = frontier in 21st century

(c.f., astrometric missions like SIM, GAIA, JASMINE)

Sun Galaxy Center

Parallax

VERA : VLBI Exploration of Radio Astrometry

Ishigaki-jima Ogasawara

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

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 systemdual-beam receivers

VERA station

reference

atmosphere

Target source

telescope

Dual-beamplatform(2.2 deg max)

Phase-referencing

Dual-beam phase compensationW49N and OH43.8-0.1 again (on 23/Jul/2002)

Phase residual : ~8 degree in RMS

~1 m

as

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

NGC 281

ρ ophS CrtOrion

NGC 1333

Solar neighborhood

VY CMa

Parallax + proper motion Proper motion

Sgr A

OH43

W49N

ON2

T Lep

SY SclR UMa

L1204

I06058

AFGL2789 I19213

G14

ON1

WB755

WB621G34 I19181

S 269 proper motionS269 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

S269Sun

GalaxyCenter

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

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

Maser locations

H2O maser parallax2.4 +/- 0.1 kpc (Nagayama+ in prep)

c.f. ) Methanol maser parallax2.57+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

Dame et al.1987Dame 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)

G14.33-0.64 & Sgr Arm

• D = 1.12 +/- 0.13 kpc (Sato et al. 2010)

G14

Sun

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 maser4 others from VLBA

• Pitch angle of Perseus arm16 +/- 3 degfour arm spiral ?

• Galactic constantsR0 = 8.4 +/- 0.6 kpcΘ0=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)20

08.5

2008

.5

2008

.10

2009

.5

2009

.12

2008

.10

2009

.5

2009

.12

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

• 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 sourcesPosition of radio sources(Menten et al. 2007)(Menten et al. 2007)

Source ISource 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)HIPPARCOSPi = 1.27 mas err 0.92mu_a -3.37 mas/yr err 1.00mu_d -4.67 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 = -3.62 LogP +1.57

（ Nakagawa et al. in prep ）

Good luck for Nano-JASMINE !