1. S/X receiver for Parkes geodetic VLBI program 29 October 2012 ATNF, Sydney 29 October 2012 Оleg Titov (Geoscience Australia)

2. 29 October 2012 Geoscience Australia IVS astrometric programs International VLBI Service (IVS) supports several observational programs (Earth Orientation Parameters; geodesy; astrometry). All in S/X Astrometric programs are designed for improvement and densification of the International Celestial Reference Frame (ICRF2, 2009) Parkes participates in the IVS astrometric programs since 2004, and contributed to ICRF2.

3. 29 October 2012 Geoscience Australia ICRF1 catalogue (1998) Geoscience Australia 20 June 2012 1.212 defining sources with the positional accuracy ~0.25 mas 2.294 “non-defining” sources 3.102 “other” sources 608 sources separated into 3 groups

4. 29 October 2012 Geoscience Australia ICRF2 catalogue (2009) Geoscience Australia 1.295 defining sources with the positional accuracy ~0.04 mas 2.922 “non-defining” sources 3.1217 VCS sources 3414 sources separated into 3 groups

5. Geoscience Australia 29 October 2012 ICRF1

6. Geoscience Australia 29 October 2012 ICRF2

7. Geoscience Australia 29 October 2012 ICRF2 7 million group delays were measured for legacy since 1979 All done in S/X

8. Geoscience Australia 29 October 2012 Accuracy for 295 ‘defining’ sources

9. Geoscience Australia 29 October 2012 Accuracy for 1217 ‘non-defining’ sources

10. 29 October 2012 Geoscience Australia ICRF2 catalogue (2009) Geoscience Australia 295 defining sources with the positional accuracy ~0.04 mas We have reached the limit of accuracy to search for hidden systematic effects

11. Geoscience Australia 29 October 2012 The Galaxy

12. Geoscience Australia 29 October 2012 Centrifugal acceleration due to rotation of the Solar system around the Galaxy center V a V a

13. 29 October 2012 Geoscience Australia Secular aberration drift Geoscience Australia Systematic proper motion (dipole effect) caused by the acceleration of the Solar system barycentre P – angle between object and the Galactic centre

14. Geoscience Australia 29 October 2012 Analytical expression for the dipole proper motion

15. 29 October 2012 Fanselow (1983) Observation Model and Parameter Partials for the JPL VLBI Parameter Estimation Software MASTERFITV1.0, JPL Publication 83-39. Bastian (1995) Eubanks et al (1995) Gwinn et al (1997) Sovers, Jacobs, Fanselow (1998) Kovalevsky (2003) MacMillan (2005) Kopeikin and Makarov (2006) References

16. 40 sources observed in more > 1,000 sessions 29 October 2012 The dipole systematic is visually detected!

17. 29 October 2012 Observed apparent proper motions

18. 29 October 2012 a = 5.3 ± 1.1  as/yr toward  = 268 ± 12°,  = -30 ± 13° The Dipole obtained from 643 radio sources

19. 29 October 2012 Geoscience Australia Interim conclusion We are able to detect a tiny systematic proper motion of the reference radio sources (up to 1 μas/year), free of the intrinsic motion caused by the relativistic jets. Potentially, we could study the dynamics of the Universe by the same way as we used to study the dynamics of the Galaxy

20. 29 October 2012 Geoscience Australia Redshift dependenceALL (643) 0<z<0.64 (128) 0.64<z<1.13 (120) 1.13<z<1.64 (132) z>1.64 (121) Amplitude (μas/y) 5.3 +/- 1.15.0 +/- 2.38.0 +/- 2.29.3 +/- 2.79.1 +/- 3.4 Direction268 +/- 12 -30 +/- 13 275 +/- 30 -27 +/- 30 295 +/- 20 -50 +/- 16 226 +/- 19 -37 +/- 18 244 +/- 21 +17 +/- 22 Weighted rms (μas/y) 20.821.216.722.221.9

21. Quadrupole systematic (2012) 29 October 2012 Mean square mplitude ~ 4.3 ± 1.4  as/year Redshift dependent

22. Astrometric stability: 0.2<z<1 Quadrupole systematic Dipole systematic

23. Covariance function Consider correlation between two point in sphere, separated by the angular distance P 29 October 2012

24. One-dimensional covariance function 29 October 2012

25. One-dimensional covariance function 29 October 2012

26. One-dimensional covariance function 29 October 2012

27. Spectra of two proper motion components

28. 29 October 2012 Spectrum of vector proper motion

29. Geoscience Australia 29 October 2012 Accuracy for 295 ‘defining’ sources

30. 643 measured proper motions DE>+40 117 0<DE<+40 247 -40<DE<0 174 DE<-40 83 More observations are required, especially, in the southern hemisphere. 29 October 2012

31. Australian (AuScope) – New Zealand network Geoscience Australia 29 October 2012

32. 12m Antenna at Patriot 5 deg/sec in azimuth, 1.5 deg/sec in elevation 29 October 2012

33. Conclusions Positions of the reference radio sources are likely to be affected by positional instabilities, random or systematic Cosmologic signals may be presented. More observations are required, especially, in the southern hemisphere. 29 October 2012

34. Plans ICRF3 to be approved by IAU GA in 2018 IVS is planning to run am intensive astrometric program since 1, July, 2013. Southern Hemisphere is the area of special attention AuScope network to play a key role Parkes (with S/X receiver) is very important for observing of weak quasars for ICRF densification 29 October 2012

35. Thank you! 29 October 2012

36. Geoscience Australia Reference frames Inertial – no acceleration of the origin, no rotation of reference axes Non-inertial – non-zero acceleration, rotation of reference axes is permitted Quasi-inertial – acceleration of the origin is permitted, no rotation of references axes

37. 29 October 2012 Geoscience Australia ICRS definition Assumption (1995) “The reference radio sources have no measurable proper motion [at the level of precision achieved to 1995]” The secular acceleration drift (dipole effect) is not considered by the current ICRS assumptions and IERS conventions - tbd

38. 29 October 2012 Proper motion in the expanding Universe (Kristian and Sachs, 1966) “Observations in cosmology” σ – Shear ω - Rotation E – electric-type gravitational waves H – magnetic-type gravitational waves

39. The Dipole obtained from 555 radio sources a = 6.4 ± 1.5  as/yr toward  = 263 ± 11°,  = -20 ± 12° 29 October 2012

40. Geoscience Australia Solution of 2010 [Titov, Lambert, Gontier, A&A (2011), 529, A91] 555 sources 0.7 +/- 1.1 μas/y -5.9 +/- 1.2 μas/y -2.2 +/- 1.2 μas/y Amplitude 6.4 +/- 1.3 μas/y RA = 263 +/- 11 DE = -20 +/- 12 chi-sq = 1.5 wrms = 23.0 μas/y Solution of 2012 643 sources 0.2 +/- 1.0 μas/y -4.5 +/- 1.1 μas/y -2.6 +/- 1.2 μas/y Amplitude 5.3 +/- 1.1 μas/y RA = 268 +/- 12 DE = -30 +/- 13 chi-sq = 1.3 wrms = 20.8 μas/y

41. Conclusions The dipole effect does exist and is aligned with the theoretical prophecy. More distant radio sources (z>1.134) look less stable. It is important for future radio ICRF realizations. Cosmologic signals may be presented. Spectroscopic observations are essential. 29 October 2012

42. Part II Spectroscopic observations of reference radio sources (mostly in the southern hemisphere) 29 October 2012

43. Team members: David Jauncey (ATNF, CSIRO) Dick Hunstead, Helen Johnston (Uni of Sydney) Tapio Pursimo (Nordic Optical Telescope) Zinovy Malkin, Kirill Maslennikov, Alexandra Boldycheva (Pulkovo Observatory) Laura Stanford (Geoscience Australia)

44. How to implement the effect? 29 October 2012

45. Two ways (at least) 1. Introduce non-zero systematic proper motion at the level of IAU Resolutions 2. Incorporate the galactocentric acceleration to the conventional group delay model (IERS Conventions) 29 October 2012

46. Conventional group delay model Titov, Astronomy Report (2011), 55(1), 95 29 October 2012