Radio spectral characteristics of the supernova remnant Puppis A and nearby sources

TL;DR

This study analyzes the spectral index distribution of supernova remnant Puppis A and nearby sources using new radio observations, revealing local spectral variations, filament interactions, and proposing some compact features as ejecta clumps.

Contribution

It provides the first detailed spectral index map of Puppis A with new observational data and identifies the nature of compact sources and filaments in the region.

Findings

Global spectral index of Puppis A is -0.563 +/- 0.013.

Detected local spectral variations and filament patterns.

Catalogued 40 new sources, questioning previous extragalactic classifications.

Abstract

This paper presents a new study of the spectral index distribution of the supernova remnant (SNR) Puppis A. The nature of field compact sources is also investigated according to the measured spectral indices. This work is based on new observations of Puppis A and its surroundings performed with the Australia Telescope Compact Array in two configurations using the Compact Array Broad-band Backend centered at 1.75 GHz. We find that the global spectral index of Puppis A is -0.563 +/- 0.013. Local variations have been detected, however this global index represents well the bulk of the SNR. At the SE, we found a pattern of parallel strips with a flat spectrum compatible with small-scale filaments, although not correlated in detail. The easternmost filament agrees with the idea that the SN shock front is interacting with an external cloud. There is no evidence of the previously suggested correlation between emissivity and spectral index. A number of compact features are proposed to be evolved clumps of ejecta based on their spectral indices, although dynamic measurements are needed to confirm this hypothesis. We estimate precise spectral indices for the five previously known field sources, two of which are found to be double (one of them, probably triple), and catalogue 40 new sources. In the light of these new determinations, the extragalactic nature previously accepted for some compact sources is now in doubt.