3D insights into SN 1987A: ALMA observations compared to hydrodynamical explosion simulations

TL;DR

This study uses high-resolution ALMA observations to map the 3D distribution of molecules in SN 1987A's ejecta and compares these with advanced hydrodynamical models, revealing insights into explosion mechanisms and progenitor characteristics.

Contribution

It provides the first detailed 3D molecular maps of SN 1987A's ejecta and compares them with state-of-the-art explosion simulations, identifying best-fit progenitor models and explosion dynamics.

Findings

Binary-merger blue supergiant models best match CO morphology.

SiO distribution indicates insufficient mixing in models.

Potential correlation between ejecta mass center and neutron-star kick direction.

Abstract

We obtain three-dimensional distributions of CO and SiO molecules from high spatial resolution (0.03--0.06") ALMA observations of SN 1987A at two different epochs. The evolution between these two epochs is consistent with homologous expansion. From these 3D maps, we reconstruct the 3D mass distributions of the ejecta in CO and SiO molecules, which we compare with those obtained by state-of-the-art, long-time hydrodynamical supernova explosion models computed with the Prometheus-HotB code for 10 different progenitors, including both red and blue supergiants. The models which best match the mass distributions correspond to explosions of binary-merger blue supergiant progenitors; at least two such models approximately reproduce the observed CO morphology. In contrast, the SiO velocity distribution and morphology are not as well reproduced in these models, indicating insufficient mixing of Si into the outer layers already at the progenitor stage. The theoretical models suggest a strong correlation between the centre of mass of the densest carbon- and oxygen-rich ejecta and the direction of the neutron-star kick. If such a correlation also applies to the CO emission in the ejecta of SN 1987A, the kick of the compact remnant is expected to point towards the observer, at an angle of approximately $45^\circ$ to the north.