Core-shifts and proper-motion constraints in the S5 polar cap sample at the 15 and 43 GHz bands
Artikel i vetenskaplig tidskrift, 2018

We have studied a complete radio sample of active galactic nuclei with the very-long-baseline-interferometry (VLBI) technique and for the first time successfully obtained high-precision phase-delay astrometry at Q band (43 GHz) from observations acquired in 2010. We have compared our astrometric results with those obtained with the same technique at U band (15 GHz) from data collected in 2000. The differences in source separations among all the source pairs observed in common at the two epochs are compatible at the 1σ level between U and Q bands. With the benefit of quasi-simultaneous U and Q band observations in 2010, we have studied chromatic effects (core-shift) at the radio source cores with three different methods. The magnitudes of the core-shifts are of the same order (about 0.1 mas) for all methods. However, some discrepancies arise in the orientation of the core-shifts determined through the different methods. In some cases these discrepancies are due to insufficient signal for the method used. In others, the discrepancies reflect assumptions of the methods and could be explained by curvatures in the jets and departures from conical jets.

Radio continuum: general

Techniques: high angular resolution

Techniques: interferometric

Quasars: general

BL Lacertae objects: general



F.J. Abellan

Universitat de Valencia

Ivan Marti-Vidal

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

J.M. Marcaide

Universitat de Valencia

J. C. Guirado

Universitat de Valencia

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 614 A74


Subatomär fysik

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik



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