European VLBI Network spectral imaging of the “compact double” radio source 2050+364 in the UHF band at 1049 MHz has resolved the HI absorbing region, and has shown a faint continuum component to the North (N), in addition to the well-known East-West double (E, W). Re-examination of VLBI continuum images at multiple frequencies suggests that 2050+364 may well be a one-sided core-jet source, which appears as a double over a limited frequency range. One of the dominant features,W, would then be the innermost visible portion of the jet, and could be at or adjacent to the canonical radio core. The other, E, is probably related to shocks at a sudden bend of the jet, towards extended steep-spectrum region N. A remarkably deep and narrow HI absorption line component extends over the entire projected extent of 2050+364. It coincides in velocity with the [OIII] optical doublet lines to within 10 kms^−1. This HI absorption could arise in the atomic cores of NLR clouds, and the motion in the NLR is then remarkably coherent both along the line-of-sight and across a projected distance of > 300 pc on the plane of the sky. Broader, shallower HI absorption at lower velocities covers only the plausible core area W. This absorption could be due to gas which is either being entrained by the inner jet or is flowing out from the accretion region; it could be related to the BLR (Refer to PDF file for exact formulas).

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This is the pre-print of an article published by EDP Sciences. The final, published version is available here: https://doi.org/10.1051/0004-6361:20053857

Reproduced with permission from Astronomy & Astrophysics, © 2006 ESO

Also archived in: arXiv: astro-ph/0510440 v1 14 Oct 2005

The European VLBI Network is a joint facility of European, Chinese, South African and other astronomy institutes funded by their national research councils. The WSRT is operated by ASTRON (The Netherlands Foundation for Research in Astronomy) with support from the Netherlands Foundation for Scientific Research (NWO). The data were correlated at the NRAO, Socorro processor. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration in the United States of America. We thank Dr. Raffaella Morganti for useful discussions, and the referee, Dr. Seiji Kameno, for a very thorough report, which has led to considerable enhancements to this paper.

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