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

The detected polarized radio emission from the remnant of SN1987A opens the possibility to unveil the structure of the pre-supernova (pre-SN) magnetic field (MF) in the circumstellar medium. Properties derived from direct measurements would be of importance for understanding the progenitor stars and their MFs. As the first step to this goal, we adopted the hydrodynamic (HD) data from an elaborated three-dimensional (3D) numerical model of SN1987A. We have developed an approximate method for 'reconstruction' of 3D MF structure inside SN remnant on the 'HD background'. This method uses the distribution of the MF around the progenitor as the initial condition. With such a 3D magnetohydrodynamic 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 MF 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-SN MF should be dominant on the length-scale of the present-day radius of SN1987A. The physical reasons for such a field are discussed.

Automated summary

The polarized radio emission from SN1987A provides the opportunity to reveal the pre-supernova magnetic field structure in the circumstellar medium. By using a three-dimensional numerical model, a method for reconstructing the 3D magnetic field structure inside the remnant has been developed. Different initial configurations of the magnetic field and the synchrotron emission structure in SN987A have been tested and compared to observations, and it has been found that the radial component of the pre-SN magnetic field dominates in SN1987A.