Small-scale structure of the SN 1006 shock with Chandra observations

The northeast shell of SN 1006 is the most probable acceleration site of high-energy electrons (up to similar to100 TeV) with the Fermi acceleration mechanism at the shock front. We resolved nonthermal. laments from thermal emission in the shell with the excellent spatial resolution of Chandra. The thermal component is extended over similar to100" (about 1 pc at 1.8 kpc distance) in width, consistent with the shock width derived from the Sedov solution. The spectrum is fitted with a thin thermal plasma of kT = 0.24 keV in nonequilibrium ionization, typical for a young supernova remnant. The nonthermal. laments are likely thin sheets with scale widths of similar to4" (0.04 pc) and similar to20" (0.2 pc) upstream and downstream, respectively. The spectra of the. laments are fitted with a power-law function of index 2.1-2.3, with no significant variation from position to position. In a standard diffusive shock acceleration model, the extremely small scale length in the upstream region requires the magnetic field nearly perpendicular to the shock normal. The injection efficiency (eta) from thermal to nonthermal electrons around the shock front is estimated to be similar to1 x 10(-3) under the assumption that the magnetic field in the upstream region is 10 muG. In the. laments, the energy densities of the magnetic field and nonthermal electrons are similar to each other, and both are slightly smaller than that of thermal electrons. These results suggest that the acceleration occurs in more compact regions with larger efficiency than suggested by previous studies.