uGMRT sub-GHz view of the Sausage cluster diffuse radio sources

TL;DR

This study uses uGMRT observations to reveal new morphological features and spectral index variations in the Sausage cluster's radio relics, enhancing understanding of their structure and formation.

Contribution

It provides new detailed morphological and spectral insights into the Sausage cluster's radio relics using uGMRT data, including the discovery of additional relics and structural features.

Findings

Variation in spectral index profiles across relics

Confirmation of an additional ~930 kpc relic in the north

Identification of a double-strand structure similar to 'Toothbrush' relic

Abstract

CIZA J2242.8+5301, or the Sausage cluster, is well studied over a range of frequencies. Since its first discovery, a lot of interesting features and unique characteristics have been uncovered. In this work, we report some more new morphological features using the uGMRT band-3 and band-4 data. In the north relic, we observe variation in spectral index profiles across the relic width from the east to west, which may indicate a decrease in downstream cooling rate in that direction. We re-confirm the presence of an additional ~ 930 kpc relic in the north. We classify the filamentary source in the downstream region to be a narrow angle tail (NAT) radio galaxy. The bright arc in the east relic shows sub-structure in the spectral index profile, which may indicate the presence of finer filaments. We further report the presence of a double-strand structure in the east relic similar to the 'Toothbrush' relic. We categorize the bright 'L' shaped structure in the southern relic to be a NAT radio galaxy, as well as trace the actual ~ 1.1 Mpc relic component. We re-confirm the existence of the faint southern extent, measuring the relic length to be ~ 1.8 Mpc. Furthermore, we suggest the southern relic to be a union of individual component relics rather than a single giant filamentary relic. Lastly, based on the morphological symmetry between northern and southern relics, we suggest a schematic shock structure associated with the merger event in an attempt to explain their formation scenario.