The supernova remnant population of the Small Magellanic Cloud

Abstract

Aims. We present a comprehensive study of the supernova remnant (SNR) population of the Small Magellanic Cloud (SMC). We measure multiwavelength properties of the SMC SNRs and compare them to those of the Large Magellanic Cloud (LMC) population.Methods. This study combines the large dataset of XMM-Newton observations of the SMC, archival and recent radio continuum observations, an optical line emission survey, and new optical spectroscopic observations. We can thus build a complete and clean sample of 19 confirmed and 4 candidate SNRs. The homogeneous X-ray spectral analysis allows to search for SN ejecta and Fe K line emission, and to measure interstellar medium (ISM) abundances. We estimate the ratio of core-collapse to type Ia supernova rates of the SMC based on the X-ray properties and the local stellar environment of each SNR. Results. After the removal of unconfirmed or misclassified objects, and the addition of two newly confirmed SNRs based on multiwavelength features, we present a final list of 21 confirmed SNRs and 2 candidates. While no Fe K line is detected even for the brightest and youngest SNR, we find X-ray evidence of SN ejecta in 11 SNRs. We estimate a ratio of 4.7 +0.6 −1.9 core-collapse supernova to every type Ia SN, three times higher than in the LMC. The difference can be ascribed to the absence of the enhanced star formation episode in the SMC, which occurred in the LMC 0.5 -1.5 Gyr ago. The hot-gas abundances of O, Ne, Mg, and Fe are 0.1 -0.2 times solar. Their ratios with respect to SMC stellar abundances reflect the effects of dust depletion and partial dust destruction in SNR shocks. We find evidence that the ambient medium probed by SMC SNRs is less disturbed and less dense on average than in the LMC, consistent with the different morphologies of the two galaxies.

Unexpected circular radio objects at high Galactic latitude

“…The morphology of the ORCs is remarkably similar to some typical supernova remnants (SNRs) (Anderson et al 2017;Bozzetto et al 2017;Green 2019;Joseph et al 2019;Maggi et al 2019). We calculate the probability that the ORCs are SNRs as follows.…”

The Rapid ASKAP Continuum Survey I: Design and first results

“…The bright nebula complex towards the top of the image is NGC 346 (also known as N66 and DEM 103), and to the lower right is N19 (DEM 32). A number of supernova remnant shells are visible, see, for example, Maggi et al (2019) for details. Figures 16 and 17 provide some comparison between images from RACS and other radio surveys.…”

Exploration of Aspherical Ejecta Properties in Type Ia Supernovae: Progenitor Dependence and Applications to Progenitor Classification

“…Analysis of SNRs on larger scales, including the Small and Large Magellanic Clouds, can reveal the SN explosion history (Maggi et al 2016(Maggi et al , 2019). The study of particular elements, e.g., Mn, can point out the major explosion mechanism (McWilliam et al 2018;de los Reyes et al 2020;Kobayashi et al 2020).…”