VERA project

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VERA project

• Mareki Honma
• (National Astronomical Observatory of Japan)
• 2/Mar/2005 _at_ Hokkaido Univ.

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Project Overview
VERA VLBI Exploration of Radio Astrometry

• The first array dedicated to VLBI astrometry
• New technique dual-beam antenna
• Target sources maser sources
• Science target to establish 3D structure and
  dynamics of the Milky Way

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Science with VERA

• Fundamental structure of the Galaxy
• Physics of Mira variables, Period-Luminosity
  Relation
• Outflows in star forming regions
• High energy object (XRB, GRB etc.)
• General relativity test

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Summary of Current status

• 2000 Construction started
• 2002 Array construction completed
• 2002 System evaluation as single dish,
  sigle-beam VLBI
• 2003 System evaluation as dual-beam VLBI
• 2004 Evaluation of astrometric precision
• Geodetic observations
• VLBI with universities
• 2003/04 Common-use (domestic only)
• 2004 project observation
• 1015 years to do astrometry of 1000 masers

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Future Extension VLBI in East Asia

• Japanese stations
• VERA, Hokkaido, Gifu,
• Yamaguchi, Kashima,
• Usuda, Tsukuba etc.
• Korea KVN 20m x 3
• (to be completed in 2007)
• China
• Shanghai, Urumqi
• ( VSOP-2)

will provide better sensitivity and better
image Science Galactic structures and AGNs
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VERA array
4 x 20m radio telescopes Completed in 2002
Iriki
Mizusawa
Ogasawara
Ishigaki
Max baseline 2300 km
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VERA telescope dual-beam antenna
Dual-beam antenna 2 receivers at focal
plane Simultaneous observations of two adjacent
sources can cancel out atmospheric
fluctuation target accuracy 10 micro-arcsec !
Schematic view of normal VLBI station and VERA
station
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Dual-beam receiving system
Dual-beam platform (Max. beam separation 2.2
deg)
dual-beam receivers
(22GHz 43GHz band receives)
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Astrometry of the Milky Way with VERA
Parallax measurement
target accuracy 10 micro-arcsec !

• VERA enables us to do astrometry of the Whole
  Milky Way Galaxy (c.f. GAIA, SIM)

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High-precision Astrometric Missions
Near-future projects for 10 micro-arcsec
astrometry
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Target source masers
Maser from outflow in SFR
H2O maser (22GHz) SiO masers (43GHz) Star
Forming Regions (H2O) AGB stars (H2O, SiO)
distribution of H2O maser sources
Maser from TX Cam
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Fundamentals of the Galaxy

• Distance to the Sgr A R0
• Galactic Rotation velocity at the Sun ?0
• Local disk density, local dark matter
• Structure of bulge and spiral arms
• Rotation curve
• ? dark matter where how much ?

Face-on view of Galactic maser distribution
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Astrometric Microlensing

• Whats Astrometric microlensing ?
• microlensing events detected through image
  position change
• Why Astrometric Microlensing ?
• 1) Large Lens size (high probability)
• 2) Independent observables
• from photometric events
• 3) Existence of high-precision missions
• in near future
• New tool to study dark object

Example of image position change in astrometric
microlensing
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Period Luminosity Relation of Mira

• Another standard cosmic candle ?
• Better understanding of stellar physics

PL relation of Mira (Feast et al 1989)
PL relation for AGBs (Wood 2000)
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High Energy Objects

• Natural laboratory of
• High Energy Physics
• X-ray binaries
• star compact objects
• (WD, NS, BH ?)
• measurement of distance
• and orbital motion
• ? mass, energy scale,
• nature of compact object

GRO 1655-40 with VLBA
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Gamma-ray burst

• Gamma-ray burst
• origin Super Nova
• relativistic jet
• (? super-luminal motion expected)

GRB030329 detected with VERA
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VERA Ishigaki-jima station

• Radio telescope
• in sub-tropical island

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General Relativity test

• Gravitational Deflection of Light by the Sun
• T(1?) / 2 (4GM / c2b)
• 1.75 arcsec for General Relativity
• Current value ? 1.000/-0.001 from VLBI
  astrometry
• (with accuracy of 1 mas)
• Expected improvement by order of 2 (accuracy 1
  mas to 10 micro-as)

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????????

• ?????????????????

10000 AU
3000 AU
W49N D 11.5 /- 1.5 kpc Gwinn et al. (1992)
OH 43.8-0.1 with VERA D 2.8 /- 0.5 kpc Honma
et al. (2005)
Vflow 200 km/s
Vflow 8 km/s
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W49N - OH43.8-0.1 pair
W49N

• Milky Way in summer

OH43