Galactic Structure seen with VLBI astrometry

Mareki HonmaMizusawa VLBI observatory, NAOJ

21/Jul/2009 @ Astrometry workshop in Socorro

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 10th anniversary symposium in 2003)

Galaxy-scale 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

Optical astrometric missions

• Satellite mission for Galaxy-scale astrometry

GAIA (ESA)2012

SIM (NASA)2015?

JASMINE (JAXA)2017?

Target accuracy is ~10 μas

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 cancelout the troposphere effect

VLBI station

reference

atmosphere

Target source

Phase-referencing VLBI

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

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

W49NON2

T Lep

SY Scl

R UMaL1204

I06058

AFGL2789I19213

G14

Distance to Orion KLAstrometry of H2O masers in

Orion KLHirota et al. (2007)

D = 437 +/- 19 pc

pi = 2.29 +/- 0.1 mas

Orion nebula with Subaru

• 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

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)– VY CMa (Choi+2009)

– Orion, Taurus, Cepheus, Ophiucus (WTTS: Menten+, Torres+, Loinard+)

see Talk by Loinard

NGC 281 & Galactic Super bubbleNGC 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/s10 deg

Galactic Longitude

300

pcHII region

HD5005

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 ?

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 kpcHonma 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)

VLBA

• 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

VLBA maser astrometry• OH (AGB)

• CH3OH, H2O (SFR)

Vlemmings et al.(2007) Xu et al. (2007)

W3

12 GHz Maser Parallaxes

• Current parallax results

• More in progress

CfA : ReidMPIfR: Menten,

BrunthalerArcetri: MoscadelliNanjing: Xu, Zheng

et al.

Combined analysis of VLBA/VERA• 18 sources published by 2008

10 VLBA Mehtanol 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

Slow rotation of HMSFR

• HMSFR appear to rotate slowly

Residual against flat rotation curvewith R0=8.5 kpc, Θ0=220 km/s

Comparison withHipparcos UVW results

Maser Astrometry with other array

• 6.7GHz Methanol maser astromerywith EVN: successfully detectedparallaxes for some sources (Rygl, Brunthaler et al.)

• 6.7G observations also on-goingwith LBA in Australia

6.7 GHz methanol will be useful probe (plenty of sources, bright, stable many stations …)

Rygl+2008, with EVN

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 astrometryinternational collaborations will be beneficial for all

Future prospectToward 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

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…