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Australian Government Geoscience Australia. Cosmologic astrometry. Yonsei University, Seoul 1 8 October 2010. 03/000. Geoscience Australia. 18 October 2010. The concept. . . B. B = 10000 km ,  = 0.03 cos sec. Geoscience Australia. 18 October 2010.

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  1. Australian Government Geoscience Australia Cosmologic astrometry Yonsei University, Seoul 18October 2010 03/000

  2. Geoscience Australia 18 October 2010

  3. The concept   B B = 10000 km,  = 0.03cos sec Geoscience Australia 18 October 2010

  4. ICRF2 defining sources 18 October 2010

  5. ICRF1 → ICRF21995 → 2010total number of objects 608 →3414number of defining sources 212 → 295formal errorσ(0) = 60 µas → 7 µas “inflated”error σ = 250 µas → 41 µas Geoscience Australia 18 October 2010

  6. Astrometry of stars (~2000 years)↓Astrometry of quasars no structure huge variable structure Geoscience Australia 18 October 2010

  7. ICRF source instability(structure) Geoscience Australia 18 October 2010

  8. Instability of the ICRFsources(2201+315) Geoscience Australia 18 October 2010

  9. Instability of ICRF sources( 2201+315, in sky plane, 2001-2004) Kellermann et al. (2004) Position angle of the brightest jet ~ 158º Geodetic VLBI: Position angle ~ 148º apparent proper motion ~ 0.6 mas/year Geoscience Australia 18 October 2010

  10. 2145+067 18 October 2010

  11. Definition of proper motion Change of position of a celestial object approximated by linear trend Geoscience Australia 18 October 2010

  12. 2145+067 18 October 2010

  13. The apparent motions look randomThe systematic has been searched since(Gwinn, Eubanks et al. 1997; MacMillan 2003) Geoscience Australia 18 October 2010

  14. Apparent motion 18 October 2010

  15. FK5 → ICRF21988 → 2010position accuracy0”.019= 19000 µas → 41 µas apparent motion accuracy700 µas/year → 10-100 µas/year Geoscience Australia 18 October 2010

  16. Assumption (1995)“The reference radio sources have no measurable proper motion [at the level of precision achieved by 1995]” Geoscience Australia 18 October 2010

  17. Possible reasons of the assumption violation 1. Secular aberration drift(Bastian, 1995; Sovers et al., 1998, Klioner, 2003) 2. Hubble constant anisotropy (Kristian and Sachs, 1966) 3. Primordial gravitational waves (Kristian and Sachs, 1966; Pyne et al., 1996) 4. Motion of the Solar system with respect CMB Kardashev (1986), Sovers et al (1998)<14 µas/year (Galaxy M81) 18 October 2010

  18. Directed towards the centre of Galaxy(RA= 270º, DE = -30º) a = V²/R 1. Centrifugal acceleration due to rotation of the Solar system around the Galaxy center Geoscience Australia 18 October 2010

  19. 1. Centrifugal acceleration due to rotation of the Solar system around the Galaxy center Geoscience Australia 18 October 2010

  20. 1. Centrifugal acceleration due to rotation of the Solar system around the Galaxy center V V a a Geoscience Australia 18 October 2010

  21. 1. All quasars are attracted by the Galactic centre Geoscience Australia 18 October 2010

  22. 1. Centrifugal acceleration due to rotation of the Solar system Volatile! Geoscience Australia 18 October 2010

  23. 2 и 3 Proper motion in the expanding Universe(Kristian and Sachs, 1966) “Observations in cosmology” 18 October 2010

  24. 2. The Hubble law The Earth H - the Hubble constant It is supposed to be isotropic for all directions on the sky 18 October 2010

  25. 2. Hubble constant anisotropy - generalised Hubble expansion 18 October 2010

  26. 2. Hubble constant anisotropy The Hubble law Anisotropic Hubble expansion and non-zero systematic 18 October 2010

  27. 3. Primordial gravitational waves (Kristian and Sachs, 1966) σ – “Shear” ω- rotation E – Electric-type gravitational waves H – Magnetic-type gravitational waves 18 October 2010

  28. 3. Primordial gravitational waves Gwinn et al (1997) – power density of gravitational waves 18 October 2010

  29. Only three reasons are considered 1.Dipole systematic2. Rotation (no physics yet)3. Gravitational waves and Hubble constant anisotropy Geoscience Australia 18 October 2010

  30. Proper motion model rotation dipole Magnetic-type Gravitational waves Electric-type gravitational waves or Hubble constant anisotropy 18 October 2010

  31. Proper motion model dipole rotation 18 October 2010

  32. Systematic effect in apparent motion 18 October 2010

  33. This is not effect of intrinsic structure! Geoscience Australia 18 October 2010

  34. ~5000 24-hour sessionssince 1980 ~6 million delays~ 3000 sourcesSoftware CALC/SOLVE (S.Lambert, A.-M. Gontier; Paris Observatory) Global solution Geoscience Australia 18 October 2010

  35. Proper motion model dipole rotation 18 October 2010

  36. Dipole effect in apparent proper motion α= 266º +/-8º δ= -18º+/- 18º A = 5.8 +/- 1.4 μas 18 October 2010

  37. Quadrupole effect in apparent proper motion 18 October 2010

  38. 18 October 2010

  39. Quadrupole effect in apparent proper motion – component E(2,1) 18 October 2010

  40. Quadrupole effect in apparent proper motion – component E(2,0) 18 October 2010

  41. Main results - Quadrupole systematic is marginal A = 3.5 +/- 0.9 μas Energy density of primordial gravitational waves Too much uncertainty!!! Geoscience Australia 18 October 2010

  42. - Galactocentric acceleration Main results Dipole effect α = 266º +/-8º δ = -18º+/- 18º A = 5.8 +/- 1.4 μas First direct identification of Galactocenrtic acceleration of the Solar system barycentre Geoscience Australia 18 October 2010

  43. Assumption (1995)“The reference radio sources have no measurable proper motion [at the level of precision achieved by 1995]” Main results Problems for ICRS definition The secular acceleration drift (dipole effect) is not taken into account by the current ICRS definition/assumption Geoscience Australia 18 October 2010

  44. Question If proper motion are real, then the reference axes are not fixed by the positions of the defining sources! How to deal with the non-zero proper motion??? 18 October 2010

  45. Conclusion • Secular aberration drift has been found. • Fundamental astrometry has a strong cosmologic component • Geodetic VLBI is able to measure apparent motion of several thousand reference radio sources and promote some fundamental discoveries about the Universe • Attract more resources (funds, grants, students) and public/media attention 18 October 2010

  46. Suggestion • Modify the IVS observational program to obtain about 3000 proper motion by 2020 (instead of 700). • This number increases very slowly, from ~500 in 2001 to ~700 in 2010. Just because existing IVS observational programs target on the well-known sources with long observational history. New sources are observed rarely. • To organize a dedicated astrometric program in the southern hemisphere. New AuScope network + New Zealand dish + Asia-Pacific network + Kokee. 18 October 2010

  47. Thank you! 18 October 2010

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