电波天文学特论（代讲）.ppt

1、VERA project,Mareki Honma (National Astronomical Observatory of Japan)2/Mar/2005 Hokkaido Univ.,Project Overview,The first array dedicated to VLBI astrometryNew technique : dual-beam antennaTarget sources : maser sources Science target : to establish 3D structure and dynamics of the Milky Way,VERA:

2、VLBI Exploration of Radio Astrometry,Science with VERA,Fundamental structure of the GalaxyPhysics of Mira variables, Period-Luminosity RelationOutflows in star forming regionsHigh energy object (XRB, GRB etc.)General relativity test,Summary of Current status,2000Construction started2002Array constru

3、ction completed2002System evaluation as single dish, sigle-beam VLBI2003System evaluation as dual-beam VLBI2004Evaluation of astrometric precisionGeodetic observationsVLBI with universities2003/04Common-use (domestic only)2004project observation1015 years to do astrometry of 1000 masers,Future Exten

4、sion: VLBI in East Asia,Japanese stationsVERA, Hokkaido, Gifu,Yamaguchi, Kashima, Usuda, Tsukuba etc.KoreaKVN：20m x 3（to be completed in 2007）China Shanghai, Urumqi(+ VSOP-2),will provide better sensitivity and better imageScience : Galactic structures and AGNs,VERA array,Iriki,Mizusawa,Ogasawara,Is

5、higaki,4 x 20m radio telescopesCompleted in 2002,Max baseline : 2300 km,VERA telescope : dual-beam antenna,Dual-beam antenna : 2 receivers at focal planeSimultaneous observations of two adjacent sources can cancel out atmospheric fluctuationtarget accuracy : 10 micro-arcsec !,Schematic view of norma

6、l VLBI station and VERA station,Dual-beam receiving system,Dual-beam platform(Max. beam separation : 2.2 deg),dual-beam receivers,(22GHz & 43GHz band receives),Astrometry of the Milky Way with VERA,VERA enables us to do astrometry of the Whole Milky Way Galaxy (c.f. GAIA, SIM),Parallax measurement,t

7、arget accuracy : 10 micro-arcsec !,High-precision Astrometric Missions,Near-future projects for 10 micro-arcsec astrometry,Target source : masers,H2O maser (22GHz) SiO masers (43GHz)Star Forming Regions (H2O)AGB stars (H2O, SiO),Maser from outflow in SFR,distribution of H2O maser sources,Maser from

8、TX Cam,Fundamentals of the Galaxy,Distance to the Sgr A* R0Galactic Rotation velocity at the Sun Local disk density, local dark matterStructure of bulge and spiral armsRotation curve dark matter : where & how much ?,Face-on view of Galactic maserdistribution,AstrometricMicrolensing,Whats Astrometric

9、 microlensing ?microlensing events detected through image position changeWhy Astrometric Microlensing ?1) Large Lens size (high probability)2) Independent observables from photometric events3) Existence of high-precision missionsin near futureNew tool to study dark object,Example of image position c

10、hangein astrometric microlensing,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),High Energy Objects,Natural laboratory of High Energy PhysicsX-ray binariesstar + compac

11、t objects(WD, NS, BH ?)measurement of distanceand orbital motionmass, energy scale, nature of compact object,GRO 1655-40 with VLBA,Gamma-ray burst,Gamma-ray burstorigin ： Super Novarelativistic jet (super-luminal motion expected),GRB030329 detected with VERA,VERA Ishigaki-jima station,Radio telescop

12、e in sub-tropical island,General Relativity test,Gravitational Deflection of Light by the Sun（+） / （ / ）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),運動学的距離決定,固有運動視線速度利用,OH 43.8-0.1 with VERAD = 2.8 +/- 0.5 kpcHonma et al. (2005),W49N : D = 11.5 +/- 1.5 kpcGwinn et al. (1992),10000 AU,3000 AU,Vflow 200 km/s,Vflow 8 km/s,W49N - OH43.8-0.1 pair,Milky Way in summer,W49N,OH43,