Upper limits on a radio halo in Abell 3667 at 1.4 GHz

TL;DR

This paper develops a new method to set upper limits on radio halo emission in galaxy cluster Abell 3667 at 1.4 GHz, providing constraints on its radio power and implications for cluster emission states.

Contribution

A novel synthetic halo modeling approach is introduced to accurately constrain radio halo presence in galaxy clusters.

Findings

Derived an upper limit on halo power: P_{1.4} ≤ 5.55 × 10^{23} W Hz^{-1}

A3667 likely resides in the 'off-state' with no diffuse radio emission

Method can be applied to other clusters for halo detection limits.

Abstract

The presence of a radio halo in the massive, merging cluster Abell 3667 has recently become a focus of debate in the literature following a putative halo detection at 2.4 GHz despite a lack of detection at a range of lower frequencies between 120 MHz and 1.8 GHz. Here we develop a new method to place limits on radio haloes via generation of a realistic synthetic halo based on the brightness distribution of real haloes. The model generated extends on previous methods in the literature producing a single elliptical halo model, capable of being injected into mosaic as well as single observations. Applying this model to the deepest data available 1.4 GHz data for A3667 we derive an upper limit halo power of P$_{1.4} \leq 5.55 \times 10^{23}$ W Hz$^{-1}$. We discuss the result in the context of current scaling relation between the X-ray and radio properties of galaxy clusters and find that the lack of a halo in A3667 places the cluster on the border of the so-called `off-state' region in which clusters are expected not to host any diffuse emission.