A global view of shocked plasma in the supernova remnant Puppis A provided by SRG/eROSITA^★

¹ Max-Planck Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
e-mail: mmayer@mpe.mpg.de
² Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ Dr. Karl Remeis Observatory, Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany

Received: 23 October 2021
Accepted: 29 March 2022

Abstract

Context. Puppis A is a medium-age supernova remnant (SNR), which is visible as a very bright extended X-ray source. While numerous studies have investigated individual features of the SNR, at this time, no comprehensive study of the entirety of its X-ray emission exists.

Aims. Using field-scan data acquired by the SRG/eROSITA telescope during its calibration and performance verification phase, we aim to investigate the physical conditions of shocked plasma and the distribution of elements throughout Puppis A. In doing so, we take advantage of the uniform target coverage, excellent statistics, and decent spatial and spectral resolution of our data set.

Methods. Using broad- and narrow-band imaging, we investigate the large-scale distribution of absorption and the plasma temperature as well as that of typical emission lines. This approach is complemented by a spatially resolved spectral analysis of the shocked plasma in Puppis A, for which we divided the SNR into around 700 distinct regions, resulting in maps of key physical quantities over its extent.

Results. We find a strong peak of foreground absorption in the southwest quadrant, which in conjunction with high temperatures at the northeast rim creates the well-known strip of hard emission crossing Puppis A. Furthermore, using the observed distribution of ionization ages, we attempt to reconstruct the age of the shock in the individual regions. We find a rather recent shock interaction for the prominent northeast filament and ejecta knot, as well as for the outer edge of the bright eastern knot. Finally, elemental abundance maps reveal only a single clear enhancement of the plasma with ejecta material, consistent with a previously identified region, and no obvious ejecta enrichment in the remainder of the SNR. Within this region, we confirm the spatial separation of silicon-rich ejecta from those dominated by lighter elements. The apparent elemental composition of this ejecta-rich region would imply an unrealistically large silicon-to-oxygen ratio when compared to the integrated yield of a core-collapse supernova. In reality, both the observed ejecta composition and their apparent distribution may be biased by the unknown location and strength of the reverse shock.