A. Pirya1, S. Nandi1, D.J. Saikia2 and M. Singh1
Abstract.
We present the results of multifrequency observations of two asymmetric,
Mpc-scale radio sources with the Giant Metrewave Radio Telescope (GMRT) and
the Very Large Array (VLA). The radio luminosity of these two sources,
J1211+743 and J1918+742, are in the Fanaroff-Riley class II (FRII) range,
but have diffuse radio components on one side of the galaxy while
the opposite component appears edge-brightened with a prominent hot-spot.
Although the absence of a hot-spot is reminiscent of FRI radio galaxies,
suggesting a hybrid morphology, the radio jet facing the diffuse lobe
in J1211+743 is similar to those in FRII radio sources, and it
is important to consider these aspects as well while classifying these sources
in the FR scheme. The observed asymmetries in these Mpc-scale sources are likely
to be largely intrinsic rather than being due to the effects of orientation
and relativistic motion. The formation of a diffuse lobe facing the radio
jet in J1211+743 is possibly due to the jet being highly dissipative.
The low-frequency spectral indices of the lobes
are in the range of approximately -0.8 to -1, while at the outer edges these
vary from approximately -0.65 to -1.05 suggesting steep injection spectral indices,
which need to be examined further from observations at even lower frequencies
by telescopes such as the LOw Frequency ARray (LOFAR).
Keywords: galaxies: active -- galaxies: jets -- galaxies: nuclei --
radio continuum: galaxies -- galaxies: individual: J1211+743 --
galaxies: individual: J1918+742
1Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263 129, India
2National Centre for Radio Astrophysics, TIFR, Pune University Campus, Post Bag 3, Pune 411 007, India