Authors:
Rioja M.J., Porcas R.W., Garrington S., Alberdi A., Saikia D.J.
Abstract:
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.
Keywords:
95.10.Jk; 95.75.Kk; 98.54.Aj; 98.54.Gr; Astrometry; Galaxies: active; Galaxies: jets; Methods: data analysis; Quasars: general; Techniques: interferometry