Murchison Widefield Array detection of steep-spectrum, diffuse, non-thermal radio emission within Abell 1127

TL;DR

This study reports the detection and detailed analysis of a steep-spectrum, diffuse non-thermal radio source in galaxy cluster Abell 1127 using MWA data, revealing its relic-like nature and cluster's disturbed state.

Contribution

The paper presents the first detection of a diffuse, steep-spectrum radio source in Abell 1127 with detailed spectral and morphological analysis using MWA Phase II and archival data.

Findings

The radio source has a spectral index of -1.83±0.29.

The source exhibits an elongated morphology with a size of 850 kpc.

The cluster is in a disturbed dynamical state, consistent with merging activity.

Abstract

Diffuse, non-thermal emission in galaxy clusters is increasingly being detected in low-frequency radio surveys and images. We present a new diffuse, steep-spectrum, non-thermal radio source within the cluster Abell 1127 found in survey data from the Murchison Widefield Array (MWA). We perform follow-up observations with the 'extended' configuration MWA Phase II with improved resolution to better resolve the source and measure its low-frequency spectral properties. We use archival Very Large Array S-band data to remove the discrete source contribution from the MWA data, and from a power law model fit we find a spectral index of $-1.83\pm0.29$ broadly consistent with relic-type sources. The source is revealed by the Giant Metrewave Radio Telescope (GMRT) at 150 MHz to have an elongated morphology, with a projected linear size of 850 kpc as measured in the MWA data. Using Chandra observations we derive morphological estimators and confirm quantitatively that the cluster is in a disturbed dynamical state, consistent with the majority of phoenices and relics being hosted by merging clusters. We discuss the implications of relying on morphology and low-resolution imaging alone for the classification of such sources and highlight the usefulness of the MHz to GHz radio spectrum in classifying these types of emission. Finally, we discuss the benefits and limitations of using the MWA Phase II in conjunction with other instruments for detailed studies of diffuse, steep-spectrum, non-thermal radio emission within galaxy clusters.