eROSITA and STAPS study of the Antlia supernova remnant

¹ Dr. Karl Remeis Observatory and Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Sternwartstraße 7, 96049 Bamberg, Germany
² Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
³ Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
⁶ INAF – Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
⁷ School of Physics and Astronomy, Yunnan University, Kunming 650500, China

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 December 2025
Accepted: 11 February 2026

Abstract

Context. We report on the study of the Antlia supernova remnant (SNR), which is an old, nearby remnant of most likely a core-collapse supernova and which has an extent of ~24° in the sky. Since being detected in the ROSAT all-sky survey, it has not been observed in its entirety until the eROSITA all-sky survey (eRASS).

Aims. The new images of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board Spectrum-RG (SRG) in X-rays covering the entire SNR and its surroundings, the newest radio polarimetry data of the Southern Twenty-Centimeter All-Sky Polarization Survey (STAPS), and additional multi-wavelength data reveal the extent of the SNR and its interaction with the environment. We can thus constrain the distance and understand the evolution of the SNR.

Methods. We created mosaic images of eRASS data and extracted X-ray spectra in the entire SNR divided into smaller regions. The spectra were compared to thermal plasma models to derive the SNR’s physical properties. From the radio polarimetry data, Faraday moment maps were created and compared to optical and X-ray emission.

Results. The X-ray emission fills the interior of the shell of the Antlia SNR, which is seen in Hα and also well traced in the Faraday maps. In addition, structures are found in the extinction and Faraday maps, which are (anti-)correlated with the X-ray emission, and suggest the existence of matter in the foreground. We thus constrain the distance to 250–450 pc, yielding a lower limit that is higher than the one suggested before. The morphology in radio, optical, and X-rays suggests that the SNR is expanding in a medium with a general density gradient, as it is located above the Galactic plane. In addition, there seems to be a denser cloud at higher latitudes, with which the outer shock wave is interacting and which causes an indentation in the outer shell. The X-ray spectra suggest that the plasma in the SNR is not in collisional ionisation equilibrium, but seems to be close to equilibrium at lower Galactic latitudes. A little enhancement in Ne or S abundance is found in some regions, though the significance is low. The Faraday moment maps from the polarisation data indicate enhanced magnetic fields along the shell, with small-scale structures that coincide with small filaments in Hα.

Conclusions. By combining large-survey data of eRASS and STAPS, we have obtained a better understanding of the morphology, physical properties, and interior features of one of the closest SNRs.