Wide-Field uGMRT band-3 Imaging of the Fields Around X-Shaped radio galaxies

Spectral properties of 4C32.25 and 4C61.23

¹ Astrophysics Research Centre, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban 4041, South Africa
² Wits Centre for Astrophysics, School of Physics, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa

^⋆ Corresponding author: edwinretana@gmail.com

Received: 28 July 2025
Accepted: 26 September 2025

Abstract

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 was 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-frequency and 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 toward 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.