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

Geoscience Australia 15 September 2005

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

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

ICRF defining sources Geoscience Australia 15 September 2005

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

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

ICRF source instability (quasar ) Geoscience Australia 15 September 2005

ICRF source instability (quasar , in plane, ) Geoscience Australia 15 September 2005 Shift ~1.2 mas ( ~3.5 cm ) other stable # 3

ICRF source instability (structure) Geoscience Australia 15 September 2005

ICRF source instability (structure) Geoscience Australia 15 September 2005

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

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

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

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

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

All networks are separated into 2 groups 1. NEOS-A/IRIS-A in 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

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

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

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

Direct adjustment AUS sessions (24 hour) 3, time delays Geoscience Australia 15 September 2005 Global CRF solutions

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) All data Black – all data; red – no IRIS-A/NEOS-A data in

Geoscience Australia 15 September 2005 Global VLBI solutions (Galaxy Acceleration, μas/y ) 207 ICRF-Ext.2199 ‘stable’120 ‘overstable’ / / / / /- 2.6 All data / / / / /- 2.4 Black – all data; red – no IRIS-A/NEOS-A data in

From proper motion Daily time series of ALL quasars in 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

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

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 +/ / /- 2.2 A2, μas/y-1.2 +/ / /- 2.7 A3, μas/y6.0 +/ / /- 2.0 V, μas/y 6.2 +/ / /- 2.3 RA231°214°209° DEC75°67°16°

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;

Geoscience Australia 15 September 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