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 !
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