EDP Sciences
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Volume 444, Number 2, December III 2005
Page(s) 443 - 454
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20041823

A&A 444, 443-454 (2005)
DOI: 10.1051/0004-6361:20041823

Large-scale motion, oscillations and a possible halo on the counter-jet side in 1803+784

S. Britzen1, 2, 3, T. P. Krichbaum1, R. G. Strom3, 4, A. Witzel1, T. W. B. Muxlow5, L. I. Matveenko6, R. M. Campbell7, W. Alef1, C. A. Hummel8, 9 and A. Zensus1

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53 121 Bonn, Germany
    e-mail: sbritzen@mpifr-bonn.mpg.de
2  Landessternwarte, Königstuhl, 69117 Heidelberg, Germany
3  ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
4  Astronomical Institute `A. Pannekoek', University of Amsterdam, The Netherlands
5  The University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Cheshire SK11 9DL, UK
6  Space Research Institute, Profsojuznaja 84/32, Moscow 117997, Russia
7  Joint Institute for VLBI in Europe, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
8  U.S. Naval Observatory, 3450 Massachusetts Avenue NW, Washington, DC 20392, USA
9  European Southern Observatory, Casilla 19001, Santiago 19, Chile

(Received 10 August 2004 / Accepted 23 August 2005 )

We present world-array VLBI observations of the blazar 1803+784 performed on May 29, 1993 at $\lambda= 18$ cm. A 17-station VLBI array, the phased VLA and the 7-station MERLIN array observed the source simultaneously for 11 h. We present the global VLBI map, the MERLIN map, and combined-array maps at different resolutions giving an overview of the morphology of 1803+784 from the inner 10 mas to ~2 arcsec. We show that the jet bends by around 90° at a core separation of about 0.5 arcsec towards the South. On larger scales, a Westerbork Synthesis Radio Telescope (WSRT) map made at a wavelength of 6 cm resolves the bridge connecting the core with the secondary component some 45'' to the south. Wiggles in the ridge of this emission suggest that, as on the 100-pc scale, the jet may also oscillate on 50-100 kpc scales. In addition to improved imaging of the southern component, the 6 cm map provides evidence for amorphous emission to the north, as well as an extended, halo-like component about the nucleus. We compare the source structure at 6 and 18 cm with the structure at 2 cm in a VLBA image obtained on November 6, 1999. Jet wiggling is clearly seen on all scales between 1 mas and 50 arcsec. We find some indication for apparent superluminal motion between ~5c and 7c for the 25 mas jet component in model-fit results for five epochs of VLBI observations performed at 6 and 18 cm. In addition, we find some evidence for further so-called stationary components in the jet of this source which will have to be confirmed in future observations spaced more densely in time. We discuss the self-similar source morphology observed from mm to cm wavelengths - namely the wiggling on all observed scales - and the implications of the deviations from self-similarity. This is the second of two papers describing the radio structure of S5 1803+784. The first presented the results of 6 years of VLBI monitoring in the X-band (Britzen et al. 2005, MNRAS, in press).

Key words: techniques: interferometric -- BL Lacertae objects: individual: 1803+784 -- radio continuum: galaxies

SIMBAD Objects

© ESO 2005