Study of some morphological features of extragalactic radio sources of FRI and FRII types

Author： Andreasyan R. Hovhannisyan M. Paronyan G. Abrahamyan H.

ISSN： 0571-7256

Source： Astrophysics, Vol.56, Iss.3, 2013-09, pp. : 382-394

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Abstract

Data on more than 650 extragalactic radio sources are used to study the distributions of the spectral indices α and elongations of radio sources in the different Fanaroff-Riley (FR) classes. No large differences are found in the distributions of the spectral indices for FRI and FRII radio sources. The following major morphological differences among objects in the different FR classes are found in a study of the distribution of the elongation of the extragalactic radio sources: (a) radio images of extragalactic FRII radio sources are more elongated on the average than those of FRI sources; (b) the extragalactic FRI radio sources can be divided into two subtypes with two distribution functions for the elongation parameter K with different maxima. Besides having different average elongations in their radio images, these two subtypes of FRI radio sources should probably also have differences in the orientations of these elongations with respect to the directions of the axes of rotation of the parent optical galaxies, which in most cases coincide with the minor optical axes of the galaxies.