Speaker
Description
Extended radio galaxies (ERGs) are powerful tracers of galaxy evolution and the interaction between radio jets and their environments. With the sensitivity and resolution of MeerKAT, it is possible to study these radio sources in greater detail than before. This study aims to identify and characterise ERGs in a 1.28 GHz field of the MeerKAT Extended Relics, Giant Halos, and Extragalactic Radio Sources (MERGHERS) survey, specifically that centered on the galaxy cluster ACT-CL J0438-5419. The raw MeerKAT data were processed using the oxkat pipeline, which included a series of data reduction, flagging, first-generation, second-generation, thirdgeneration calibration, and imaging. Primary beam corrections and astrometric checks were applied. A cleaned catalogue of 49 ERGs was built through a combination of automated source detection and visual inspection. Cross-matching with RACS, SUMSS, and GLEAM-X allowed us to compare the radio sources and measure their integrated spectral indices. The DECaLS and AllWISE surveys were used to identify optical and infrared hosts, and to obtain photometric redshifts where available. In-band spectral index maps were produced from sub-band images at 1.0, 1.2, and 1.4 GHz to investigate spatial spectral variations within the sources. The results show a diverse set of radio morphologies, including 3 FRI, 22 FRII, 6 head-tail (HT), 4 wide-angle tail (WAT), 1 Z-shaped, and 13 unclassified sources. A total of 25 hosts were identified in the optical/infrared, with photometric redshifts for 17 of them. Our findings reveal that the FRII population dominates the field and tends to have higher radio luminosities, while some HT and FRII sources are detected at redshifts above 1.25. The spectral index (α), which describes how a source radio flux density changes with frequency, is a key tracer of the underlying emission processes. The in-band spectral index maps reveal the expected trend of steepening (α À ´0.5) in the outer lobes, consistent with synchrotron ageing of electrons, while flatter spectra (α Á ´0.5) appear near the cores, marking regions of ongoing jet activity. This work demonstrates the ability of MeerKAT to resolve faint and complex ERG structures. By combining visual classification, cross-matching, and spectral mapping, we show that source morphology and spectral properties vary with environment. FRI and WAT radio sources are typically found in denser regions, while most FRII sources are found in the field. These findings provide a foundation for expanding the analysis to the full MERGHERS Tier 1 sample, enabling comparisons across multiple fields to better understand how the environment influences the evolution of extended radio galaxies.