Volume 514 - High Energy Astrophysics in Southern Africa 2025 (HEASA2025) - Active Galactic Nuclei
The study of extended radio galaxies in MERGHERS fields
B. Mthembu
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Abstract
We present a concise proceedings summary of our study of extended radio galaxies (ERGs) in the
MeerKAT Exploration of Relics, Giant Halos, and Extragalactic Radio Sources (MERGHERS)
Tier 1 field centred on ACT-CL J0438−5419 using MeerKAT L-band data at 1.28 GHz. Raw
visibilities were processed with the oxkat pipeline through 1GC–3GC calibration and imaging,
followed by primary-beam correction, astrometric checks, and sub-band imaging for in-band spectral
index mapping. A cleaned catalogue of ERGs was assembled via PyBDSF and visual inspection.
Cross-matching with RACS, SUMSS, and GLEAM-X provided broad-band fluxes; DECaLS and
AllWISE enabled host identification and photometric redshifts. We report a morphology mix
dominated by FRII sources, with FRI, WAT, HT, Z-shaped and unclassified sources also present.
In-band spectral index maps show the expected steepening in outer lobes (𝛼 ≲ −0.5) and flatter
spectra near cores, consistent with ongoing particle injection. We comment on environment for
cluster vs field sources and outline future spectro-polarimetric extensions to the full MERGHERS
sample.
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