Pj. Gopal-kirshna,"wiita, Extragalactic radio sources with hybrid morphology: implications for the Fanaroff-Riley dichotomy, ASTRON ASTR, 363(2), 2000, pp. 507-516
We provide observational and theoretical perspectives on the currently much
debated issue of the Fanaroff-Riley (FR) morphological dichotomy of extrag
alactic radio sources. In this context we introduce a new, albeit rare, cla
ss of double radio sources in which the two lobes exhibit clearly different
FR morphologies. It is argued that such 'HYbrid MOrphology Radio Sources',
or HYMORS, could be used to effectively constrain the theoretical mechanis
ms proposed for the FR dichotomy. Basically, the existence of HYMORS suppor
ts explanations for the FR dichotomy based upon jet interaction with the me
dium external to the central engine, and appears quite difficult to reconci
le with the class of explanations that posit fundamental differences in the
central engine, such as black hole spin or jet composition, to be responsi
ble for the two FR classes of double radio sources.