1. 03/000 Statistical properties of CRF solution from VLBI data analysis Oleg Titov Australian Government Geoscience Australia GAIA-2005, Dresden, 15-16, September 2005

2. Geoscience Australia 15 September 2005

3. Selection of radiosources Geoscience Australia 15 September 2005 1.ICRF (Ma et al., 1998) 2.Feissel-Vernier (2003) 3.Structure index (Fey & Charlot, 1997; 2000) A set of reference quasars to be fixed

4. ICRF catalogue (1998) Geoscience Australia 15 September 2005 1.212 defining sources with position accuracy ~0.4 mas 2.294 candidate sources 3.102 other sources 608 sources separated into 3 groups

5. ICRF defining sources Geoscience Australia 15 September 2005

6. Feissel-Vernier (2003) Geoscience Australia 1.199 ‘stable’ sources (groups 1 and 2) 2.7 ‘unstable’ sources (group 3) 3.156 ‘highly unstable or drifting’ sources (group 4) 362 pre-selected sources separated into 4 groups 15 September 2005

7. The lists are not consistent !!! Geoscience Australia 15 September 2005 81 ‘stable’ sources are ‘defining’ and 49 ‘other’

8. ICRF source instability (quasar 2201+315) Geoscience Australia 15 September 2005

9. ICRF source instability (quasar 2201+315, in plane, 2001-2004) Geoscience Australia 15 September 2005 Shift ~1.2 mas ( ~3.5 cm ) other stable # 3

10. ICRF source instability (structure) Geoscience Australia 15 September 2005

11. ICRF source instability (structure) Geoscience Australia 15 September 2005

12. ICRF source instability (flux density by Esko Valtaoja, Turku Observatory) Geoscience Australia 15 September 2005

13. - GSFC, USNO, BKG, MAO, AUS,... Geoscience Australia 15 September 2005 Global CRF solutions from VLBI

14. - AUS (Geoscience Australia) - OCCAM v 6.1 - VLBI data from 1979 till 2004 - 859 quasars in initial catalogue - Geoscience Australia 15 September 2005 Global CRF solutions

15. All radiosources are separated into 3 groups 1. Global imposed by NNR (ICRF) 2. Global without NNR 3. Local Geoscience Australia 15 September 2005 Global VLBI solutions

16. All radiosources are separated into 3 groups 1. 207 ICRF-Ext.2 ‘defining’ sources 2. 199 ‘stable’ sources 3. 120 ‘overstable’ sources Geoscience Australia 15 September 2005 Global VLBI solutions

17. All networks are separated into 2 groups 1. NEOS-A/IRIS-A in 1983-2001 limited number (332) of comparatively bright sources presumably in the Northern hemisphere ( δ>-30°) 2. all other networks (659 sources) Geoscience Australia 15 September 2005 Global VLBI solutions

18. The acceleration effect estimates are used as indicator for the CRF solutions stability 3,208.197 time delays Geoscience Australia 15 September 2005 Global VLBI solutions

19. Acceleration of the Solar system due to Galaxy rotation Geoscience Australia 15 September 2005

20. 1. Direct adjustment (one-step) (source positions are estimated as global parameters for stable sources and daily parameters for unstable sources) 2. From apparent proper motion (two-step) (source positions and apparent proper motions are estimated as global parameters for selected sources) Geoscience Australia 15 September 2005 Acceleration of the Solar system due to Galaxy rotation

21. Direct adjustment AUS 1979-2004 3199 sessions (24 hour) 3,208.197 time delays Geoscience Australia 15 September 2005 Global CRF solutions

22. Geoscience Australia 15 September 2005 Global VLBI solutions (the number of global radiosources) 207 ICRF-Ext.2 (with NNR) 199 ‘stable’ (with NNR) 120 ‘overstable’ (with NNR) 1990- 2004 627 573 566 492 485 All data 628 574 567 493 486 Black – all data; red – no IRIS-A/NEOS-A data in 1983-2001

23. Geoscience Australia 15 September 2005 Global VLBI solutions (Galaxy Acceleration, μas/y ) 207 ICRF-Ext.2199 ‘stable’120 ‘overstable’ 1990- 2004 20.7 +/- 2.6 19.7 +/- 2.1 11.7 +/- 2.4 14.8 +/- 2.4 8.9 +/- 2.6 All data 16.5 +/- 2.2 22.1 +/- 1.7 10.5 +/- 2.0 12.3 +/- 2.2 6.2 +/- 2.4 Black – all data; red – no IRIS-A/NEOS-A data in 1983-2001

24. From proper motion Daily time series of ALL quasars in 1979- 2005 separated into three equal groups 143 apparent proper motion (at least 20 sessions with at least 20 scans) including stable and unstable. Geoscience Australia 15 September 2005 USNO global VLBI solution 2005

25. 106 radiosource proper motions were used for estimation of the Galaxy acceleration effect Geoscience Australia 15 September 2005 USNO global VLBI solution 2005 V = 9.7 +/- 2.3 μas/y

26. Geoscience Australia 15 September 2005 USNO global VLBI solution 2005 AUS 2005 (120 ‘overstable’) AUS 2005 (199 ‘stable’) USNO 2005 A1, μas/y-1.0 +/- 1.3-3.3 +/- 1.0-8.2 +/- 2.2 A2, μas/y-1.2 +/- 1.2-2.2 +/- 1.0-4.5 +/- 2.7 A3, μas/y6.0 +/- 2.59.7 +/- 2.22.6 +/- 2.0 V, μas/y 6.2 +/- 2.410.5 +/- 2.09.7 +/- 2.3 RA231°214°209° DEC75°67°16°

27. Problems Geoscience Australia 19 September 2005 extended and stable radiosource can become unstable any time; positions of extended radiosources observed by different networks can be inconsistent;

28. Geoscience Australia 15 September 2005 1. VLBI data before 1990 are not reliable 2. VLBI subnetworks produce different results 3. New strategy for selection of stable radiosources is wanted 4. More radiosource are wanted 5. Effect of the Galaxy acceleration is volatile 6. Hopefully, it can be detected by 2010 Conclusion