Some properties of synchrotron radio and inverse-Compton gamma-ray images of supernova remnants

The synchrotron radio maps of supernova remnants (SNRs) in uniform interstellar medium and interstellar magnetic field (ISMF) are analysed, allowing different ‘sensitivity’ of injection efficiency to the shock obliquity. The very-high energy γ-ray maps due to inverse Compton process are also synthesized. The properties of images in these different wavelength bands are compared, with particulr emphasis on the location of the bright limbs in bilateral SNRs. Recent H.E.S.S. observations of SN 1006 show that the radio and IC γ-ray limbs coincide, and we found that this may happen if: i) injection is isotropic but the variation of the maximum energy of electrons is rather quick to compensate for differences in magnetic field; ii) obliquity dependence of injection (either quasi-parallel or quasi-perpendicular) and the electron maximum energy is strong enough to dominate magnetic field variation. In the latter case, the obliquity dependences of the injection and the maximum energy should not be opposite. We argue that the position of the limbs alone and even their coincidence in radio, X-rays and γ-rays, as it is discovered by H.E.S.S. in SN 1006, cannot be conclusive about the dependence of the electron injection efficiency, the compression/amplification of ISMF and the electron maximum energy on the obliquity angle.