Diffuse galaxy cluster emission at 168 MHz within the Murchison Widefield Array Epoch of Reionization 0-hour field

TL;DR

This study uses the Murchison Widefield Array at 168 MHz to detect and analyze diffuse radio emissions in galaxy clusters, discovering new halos, relics, and candidates, and examining their properties and scaling relations.

Contribution

First detection of multiple new diffuse radio sources in galaxy clusters at 168 MHz, expanding the known population and analyzing their spectral and scaling properties.

Findings

29 sources of interest detected, including new halos and relics.

Some sources exhibit ultra-steep spectra, e.g., halo in Abell 0141.

Detected sources are consistent with established scaling relations.

Abstract

We detect and characterise extended, diffuse radio emission from galaxy clusters at 168 MHz within the Epoch of Reionization 0-hour field: a $45^\circ \times 45^\circ$ region of the southern sky centred on R.~A.${}= 0^\circ$, decl.${}=-27^\circ$. We detect 29 sources of interest; a newly detected halo in Abell 0141; a newly detected relic in Abell 2751; 4 new halo candidates and a further 4 new relic candidates; and a new phoenix candidate in Abell 2556. Additionally, we find 9 clusters with unclassifiable, diffuse steep-spectrum emission as well as a candidate double relic system associated with RXC J2351.0-1934. We present measured source properties such as their integrated flux densities, spectral indices ($\alpha$, where $S_\nu \propto \nu^\alpha$), and sizes where possible. We find several of the diffuse sources to have ultra-steep spectra including the halo in Abell 0141, if confirmed, showing $\alpha \leq -2.1 \pm 0.1$ with the present data making it one of the steepest-spectrum haloes known. Finally, we compare our sample of haloes with previously detected haloes and revisit established scaling relations of the radio halo power ($P_{1.4}$) with the cluster X-ray luminosity ($L_{\mathrm{X}}$) and mass ($M_{500}$). We find that the newly detected haloes and candidate haloes are consistent with the $P_{1.4}$-$L_{\mathrm{X}}$ and $P_{1.4}$-$M_{500}$ relations, and see an increase in scatter in the previously found relations with increasing sample size likely caused by inhomogeneous determination of $P_{1.4}$ across the full halo sample. We show that the MWA is capable of detecting haloes and relics within most of the galaxy clusters within the Planck catalogue of Sunyaev-Zel'dovich sources depending on exact halo or relic properties.