Pilot study and early results of the Cosmic Filaments and Magnetism Survey with Nenufar: the Coma cluster field

TL;DR

This paper reports the first low-frequency detection of the Coma cluster's radio halo and relic using NenuFAR, demonstrating its potential for studying cosmic filaments and magnetic fields despite technical challenges.

Contribution

It presents the initial results of NenuFAR's pilot survey, including the first confirmed low-frequency detection of key features in the Coma cluster, and discusses data reduction techniques.

Findings

Detected radio halo at 34.4 MHz with 106.3 Jy flux

Detected radio relic at 34.4 MHz with 102.0 Jy flux

Identified technical challenges in data reduction and solutions

Abstract

NenuFAR, the New Extension in Nancay Upgrading LOFAR, is currently in its early science phase. It is in this context that the Cosmic Filaments and Magnetism Pilot Survey is observing sources with the array as it is still under construction - with 57 (56 core, 1 distant) out of a total planned 102 (96 core, 6 distant) mini-arrays online at the time of observation - to get a first look at the low-frequency sky with NenuFAR. One of its targets is the Coma galaxy cluster: a well-known object, host of the prototype radio halo. It also hosts other features of scientific import, including a radio relic, along with a bridge of emission connecting it with the halo. It is thus a well-studied object. In this paper, we show the first confirmed NenuFAR detection of the radio halo and radio relic of the Coma cluster at 34.4 MHz, with associated intrinsic flux density estimates: we find an integrated flux value of 106.3 +- 3.5 Jy for the radio halo, and 102.0 +- 7.4 Jy for the radio relic. These are upper bound values, as they do not include point-source subtraction. We also give an explanation of the technical difficulties encountered in reducing the data, along with steps taken to resolve them. This will be helpful for other scientific projects which will aim to make use of standalone NenuFAR imaging observations in the future.