Paper detail

Wide-field GMRT imaging of X-shaped Radio-Galaxies: Spectral properties of 4C32.25 and 4C61.23

We present wide-field upgraded Giant Metrewave Radio Telescope (uGMRT) images of the fields around the X-shaped radio-galaxies (XRGs) 4C32.25, 4C61.23, and MRC 2011-298 obtained at 400 MHz. The observations are calibrated using the extreme peeling method to account for direction-dependent effects across the field of view, as previously applied to Low-frequency array (LOFAR) data. Our 400 MHz images capture in fine detail the radio-morphology of the XRGs, as well as other serendipitous radio-sources located in these fields. We use these images along with archival low-frequencyand high-frequency radio data to investigate the spectral properties of the XRGs 4C32.25 and 4C61.23. Under the assumption of conditions corresponding to the maximum radio-source age, we estimate the spectral ages of both the primary lobes and the wings. These ages indicate that the wings are the oldest component of the XRGs and are a product of past radio activity. Moreover, we have used the radio images available to derive high-resolution spectral index maps for these two XRGs. We find that the spectral index steepens from the primary lobes towards the wings, consistent with our spectral age estimates. These results suggest that precessional and backflow models explain the X-shaped radio-morphology of 4C32.25 and 4C61.23, respectively. Finally, taking advantage of our wide-area images, we identify several serendipitous diffuse radio-sources located in our XRG fields and cross-reference them with previous surveys.