- On the way to global phase-delay astrometry,
E. Ros, J.M. Marcaide, J.C. Guirado, M.A. Pérez-Torres
Proceedings of the 14th Working Meeting on European VLBI for
Geodesy and Astrometry, eds. Tomasi, P., Mantovani, F.,
Pérez-Torres, M.A.,
Istituto di Radioastronomia/CNR, Bologna, Italy, 145-150 (2000)
[ PostScript ]
- Abstract
The use of the phase-delay improves substantially the
accuracy obtained in VLBI astrometry
with respect to the group-delay observable. Recently,
Ros et al. (1999) have extended the related
phase-connection technique to a triangle of
radio sources with relative separations up to 6.8o
(the S5 sources BL 1803+784/QSO 1928+738/BL 2007+777).
This technique has
also been extended for separations up to 15o in the studies
of the pair of S5 radio sources QSO 1150+812/BL 1803+784
(Pérez-Torres et al. 2000).
We are carrying out a
long-term astrometric programme at 8.4, 15, and 43 GHz to determine the
absolute kinematics of radio source components in the
13 members of the complete S5 polar cap sample.
For each epoch, all the radio sources are observed at the same frequency
for 24 hours in total.
Bootstrapping
techniques are used to phase-connect the data jointly for the
13 objects throughout the observations. An accurate
registration of the maps of the radio sources at different
frequencies will allow a study
of jet components with unprecedented precision and provide
spectral information.
This observing scheme could be extended in the future to other regions
of the sky and eventually lead to global phase-delay astrometry.
Eduardo Ros
ros@mpifr-bonn.mpg.de