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

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.

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

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

Geoscience Australia 29 October 2012 ICRF1

Geoscience Australia 29 October 2012 ICRF2

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

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

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

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

Geoscience Australia 29 October 2012 The Galaxy

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

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

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

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

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

29 October 2012 Observed apparent proper motions

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

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

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 +/ / / / /- 3.4 Direction268 +/ / / / / / / / / /- 22 Weighted rms (μas/y)

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

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

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

One-dimensional covariance function 29 October 2012

One-dimensional covariance function 29 October 2012

One-dimensional covariance function 29 October 2012

Spectra of two proper motion components

29 October 2012 Spectrum of vector proper motion

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

643 measured proper motions DE> <DE< <DE<0 174 DE< More observations are required, especially, in the southern hemisphere. 29 October 2012

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

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

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

Plans ICRF3 to be approved by IAU GA in 2018 IVS is planning to run am intensive astrometric program since 1, July, 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

Thank you! 29 October 2012

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

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

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

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

Geoscience Australia Solution of 2010 [Titov, Lambert, Gontier, A&A (2011), 529, A91] 555 sources 0.7 +/- 1.1 μas/y /- 1.2 μas/y /- 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 sources 0.2 +/- 1.0 μas/y /- 1.1 μas/y /- 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

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

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

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)

How to implement the effect? 29 October 2012

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

Conventional group delay model Titov, Astronomy Report (2011), 55(1), October 2012