A Hard (X-ray) Look at the SW Region of SNR RCW 86

That SNRs accelerate particles to CR energies is no longer in doubt, but there are many questions yet to be answered. We still lack detailed knowledge about the efficiency of the process of particle acceleration at SNR shocks, the effect of CR production on the evolution of SNRs, and the properties of magnetic fields in these systems and how these are amplified. In order to address these outstanding issues, we have observed the SW region of SNR RCW 86 with NuSTAR, in two segments totalling 250 ks, approximately. These observations have allowed us to: (1) determine the morphology of the non-thermal X-ray emission in this region in the NuSTAR band, and contrast it to observations with XMM-Newton and Chandra; (2) constrain the spectral shape of the electron population that underlies the non-thermal emission. Our analysis suggests the morphology of the source in hard X-rays closely resembles the hard X-ray emission detected with Chandra and XMM-Newton in this region. This suggests, as expected, that the X-ray emission above 3 keV is dominated by non-thermal emission from relativistic electrons. The fact that the NuSTAR detected synchrotron emission is not confined to the apparent location of the forward shock of SNR, but instead towards the inside of the thermal emission detected with XMM and Chandra, plays an important role in understanding the puzzle of this region. Here, we report on our observations and interpretation of these.