Aspect angle for interstellar magnetic field in SN 1006

TL;DR

This paper introduces a new method to estimate the interstellar magnetic field's aspect angle in SN 1006 by comparing observed and simulated radio maps, revealing insights into the magnetic field orientation and electron injection processes.

Contribution

The authors develop a novel azimuthal profile-based technique to determine the magnetic field orientation in supernova remnants, applied to SN 1006 with implications for injection models.

Findings

Best-fit aspect angle for isotropic injection: 70°

Best-fit aspect angle for quasi-perpendicular injection: 64°

Quasi-parallel injection model is inconsistent with observed morphology

Abstract

A number of important processes taking place around strong shocks in supernova remnants (SNRs) depend on the shock obliquity. The measured synchrotron flux is a function of the aspect angle between interstellar magnetic field (ISMF) and the line of sight. Thus a model of non-thermal emission from SNRs should account for the orientation of the ambient magnetic field. We develop a new method for the estimation of the aspect angle, based on the comparison between observed and synthesized radio maps of SNRs, making different assumptions about the dependence of electron injection efficiency on the shock obliquity. The method uses the azimuthal profile of radio surface brightness as a probe for orientation of ambient magnetic field because it is almost insensitive to the downstream distribution of magnetic field and emitting electrons. We apply our method to a new radio image of SN 1006 produced on the basis of archival VLA and Parkes data. The image recovers emission from all spatial structures with angular scales from few arcseconds to 15 arcmin. We explore different models of injection efficiency and find the following best-fitting values for the aspect angle of SN 1006: phi=70 +/- 4.2 deg if the injection is isotropic, phi=64 +/- 2.8 deg for quasi-perpendicular injection (SNR has an equatorial belt in both cases) and phi=11 +/- 0.8 deg for quasi-parallel injection (polar-cap model of SNR). In the last case, SN 1006 is expected to have a centrally-peaked morphology contrary to what is observed. Therefore, our analysis provides some indication against the quasi-parallel injection model.