Phase-reference mapping of a weak-cored double-lobed source in the 1636+473 system using MERLIN and Global VLBI

We present maps and astrometric results from first epoch, simultaneous MERLIN and Global VLBI observations of the very weak core of a double-lobed radio source, using as reference the bright, compact, flat-spectrum quasar 1636+473 A, 20 arcsec away. The observations were made in May 1995 at 5 GHz. T...

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Bibliographic Details
Published in:New astronomy reviews 1999, Vol.43 (8), p.593-597
Main Authors: Rioja, M.J, Porcas, R.W, Garrington, S, Alberdi, A, Saikia, D.J
Format: Article
Language:English
Subjects:
Astrometry
Galaxies: active
Galaxies: jets
Methods: data analysis
Quasars: general
Techniques: interferometry
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Summary:We present maps and astrometric results from first epoch, simultaneous MERLIN and Global VLBI observations of the very weak core of a double-lobed radio source, using as reference the bright, compact, flat-spectrum quasar 1636+473 A, 20 arcsec away. The observations were made in May 1995 at 5 GHz. The phase-referenced VLBI map of the weak core, of resolution 1.5 mas, contains a high percentage of the core flux density seen in the MERLIN map. Further hybrid mapping iterations reveal a faint, one-sided core extension on the same side as the MERLIN jet. We explore the effect of both temporal and other coherence losses on the phase-reference map. We relate our results to the structural asymmetry in weak AGN cores within the context of unification models.
ISSN:1387-6473
1872-9630
DOI:10.1016/S1387-6473(99)00060-3