文章基本信息

标题：Core-shifts and proper-motion constraints in the S5 polar cap sample at the 15 and 43 GHz bands
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作者：F. J. Abellán ; I. Martí-Vidal ; J. M. Marcaide 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：614
DOI：10.1051/0004-6361/201731869
语种：English
出版社：EDP Sciences
摘要：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 atQband (43 GHz) from observations acquired in 2010. We have compared our astrometric results with those obtained with the same technique atUband (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 1σlevel betweenUandQbands. With the benefit of quasi-simultaneousUandQband 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.
关键词：Key wordsenastrometrytechniques: interferometricquasars: generalBL Lacertae objects: generalradio continuum: generaltechniques: high angular resolution