A multifrequency study of giant radio sources - I. Low-frequency Giant Metrewave Radio Telescope observations of selected sources

We present low-frequency observations with the Giant Metrewave Radio Telescope of a sample of giant radio sources, and high-frequency observations of three of these sources with the Very Large Array. From multifrequency observations of the lobes, we estimate the magnetic field strengths using three different approaches, and show that these differ at most by a factor of similar to 3. For these large radio sources, the inverse-Compton losses usually dominate over synchrotron losses when estimates of the classical minimum energy magnetic field are used, consistent with earlier studies. However, this is often not true if the magnetic fields are close to the values estimated using the formalism of Beck & Krause. We also examine the spectral indices of the cores and any evidence of recurrent activity in these sources. We probe the environment using the symmetry parameters of these sources and suggest that their environments are often asymmetric on scales of similar to 1 Mpc, consistent with earlier studies.