Issue |
A&A
Volume 614, June 2018
|
|
---|---|---|
Article Number | A74 | |
Number of page(s) | 11 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201731869 | |
Published online | 15 June 2018 |
Core-shifts and proper-motion constraints in the S5 polar cap sample at the 15 and 43 GHz bands
1
Departament d’Astronomia i Astrofísica, Universitat de València,
C/Dr. Moliner 50,
46100
Burjassot, Spain
e-mail: francisco.abellan@uv.es
2
Department of Earth, Space and Environment, Chalmers University of Technology, Onsala Space Observatory,
43992
Onsala, Sweden
3
Observatori Astronòmic, Universitat de València, Parc Científic,
C. Catedrático José Beltrán 2,
46980
Paterna,
València, Spain
Received:
31
August
2017
Accepted:
16
February
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.
Key words: astrometry / techniques: interferometric / quasars: general / BL Lacertae objects: general / radio continuum: general / techniques: high angular resolution
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.