Hybrid morphology radio sources from the FIRST survey

Free access article

Issue		A&A Volume 447, Number 1, February III 2006


Page(s)		63 - 70
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20053996

A&A 447, 63-70 (2006)
DOI: 10.1051/0004-6361:20053996

Hybrid morphology radio sources from the FIRST survey

M. P. Gawronski, A. Marecki, M. Kunert-Bajraszewska and A. J. Kus

Torun Centre for Astronomy, N. Copernicus University, 87-100 Torun, Poland
e-mail: amr@astro.uni.torun.pl

(Received 5 August 2005 / Accepted 13 September 2005 )

Abstract
The so-called HYbrid MOrphology Radio Sources (HYMORS) are a class of objects that appear to have a mixed Fanaroff-Riley (FR) morphology in a single object; i.e. a HYMORS has an FR I-type lobe on one side of its nucleus and an FR II-type lobe on the other side. Because of this unique feature and given that the origin of the FR morphological dichotomy is still unclear, HYMORS may possibly play a crucial role in our understanding of the FR-dichotomy. As the number of known HYMORS is quite small, we aimed to increase that number by inspecting a few areas of the sky covered by the VLA FIRST survey and by selecting 21 HYMORS candidates based on the morphology shown in the FIRST images. They were observed with the VLA in B-conf. at 4.9 GHz. Three objects from the initial sample turned out to be actual HYMORS and two others very likely to fulfill the criteria. These five were subsequently re-observed with the VLA in A-conf. at 1.4 GHz. Our results provide strong support to the findings of Gopal-Krishna & Wiita (2000, A&A, 363, 507), namely that there are two different kinds of jets in HYMORS; consequently, the existence of FR-dichotomy as a whole is difficult to reconcile with the class of explanations that posit fundamental differences in the central engine.

Key words: radio continuum: galaxies -- galaxies: active -- galaxies: jets -- galaxies: nuclei

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