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The Australia Telescope National Facility Colloquium
15:30-16:30 Wed 24 Sep 2008

ATNF Marsfield Lecture Theatre

Oleg Titov

(Geoscience Australia, Canberra)

Systematic proper motion of distant radio sources from geodetic VLBI data - Oleg Titov Colloquium

The motion of relativistic jets from active extragalactic nuclei can reach several hundred microarcseconds per year and mimic proper motion of the distant radio sources observed by geodetic Very Long Baseline Interferometry (VLBI) networks. Such apparent proper motion of individual quasars is not correlated and its magnitude reaches several hundred µas/year. The effect of secular aberration drift induced by the rotation of the Solar system around the centre of the Galaxy of magnitude 4-5 µas/year has been predicted as the first degree vector spherical harmonic. In addition, the Universe expansion anisotropy and primordial gravitational waves can cause additional systematic effects described by the second degree vector spherical harmonic. About 4 million high precision geodetic VLBI observations (group delays) of about 1500 quasars have been processed to search for the systematic effects. It was found that the spherical harmonics of the first and second degree are statistically significant. However, an asymmetric distribution of the observed radio sources results in essential correlation between the estimated parameters. A dedicated program for observations of radio sources in the southern hemisphere should be initiated.

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