Hydrodynamic evolution of Sgr A East: the imprint of a supernova remnant in the Galactic Centre

Abstract

ABSTRACT We perform three-dimensional numerical simulations to study the hydrodynamic evolution of Sgr A East, the only known supernova remnant (SNR) in the centre of our Galaxy, to infer its debated progenitor supernova (SN) type and its potential impact on the Galactic Centre environment. Three sets of simulations are performed, each of which represents a certain type of SN explosion (SN Iax, SN Ia, or core-collapse SN) expanding against a nuclear outflow of hot gas driven by massive stars, whose thermodynamical properties have been well established by previous work and fixed in the simulations. All three simulations can simultaneously roughly reproduce the extent of Sgr A East and the position and morphology of an arc-shaped thermal X-ray feature, known as the ‘ridge’. Confirming previous work, our simulations show that the ridge is the manifestation of a strong collision between the expanding SN ejecta and the nuclear outflow. The simulation of the core-collapse SN, with an assumed explosion energy of 5 × 1050 erg and an ejecta mass of 10 M⊙, can well match the X-ray flux of the ridge, whereas the simulations of the SN Iax and SN Ia explosions underpredict its X-ray emission, due to a smaller ejecta mass. All three simulations constrain the age of Sgr A East to be ≲1500 yr and predict that the ridge should fade out over the next few hundred years. We address the implications of these results for our understanding of the Galactic Centre environment.