Polarized radio emission unveils the structure of the pre-supernova circumstellar magnetic field and the radio emission in SN1987A

TL;DR

This study uses polarized radio emission data and 3-D magneto-hydrodynamic modeling to reconstruct the pre-supernova magnetic field structure of SN1987A, revealing a dominant radial magnetic component.

Contribution

It introduces an approximate method to reconstruct the 3-D magnetic field inside a supernova remnant based on hydrodynamic models and polarization data, advancing understanding of pre-supernova magnetic environments.

Findings

The radial magnetic field component dominates in the pre-supernova environment.

The polarization maps successfully match observations, validating the model.

The method provides insights into the magnetic field structure influencing supernova evolution.

Abstract

The detected polarized radio emission from remnant of SN1987A opens the possibility to unveil the structure of the pre-supernova magnetic field in the circumstellar medium. Properties derived from direct measurements would be of importance for understanding the progenitor stars and their magnetic fields. As the first step to this goal, we adopted the hydrodynamic data from an elaborated three-dimensional (3-D) numerical model of SN1987A. We have developed an approximate method for `reconstruction' of 3-D magnetic field structure inside supernova remnant on the `hydrodynamic background'. This method uses the distribution of the magnetic field around the progenitor as the initial condition. With such a 3-D magneto-hydrodynamic model, we have synthesized the polarization maps for a number of SN1987A models and compared them to the observations. In this way, we have tested different initial configurations of the magnetic field as well as a structure of the synchrotron emission in SN987A. We have recovered the observed polarization pattern and we have found that the radial component of the ambient pre-supernova magnetic field should be dominant on the length-scale of the present-day radius of SN1987A. The physical reasons for such a field are discussed.