FUSE Observation of the Non-Radiative Collisionless Shock in the Remnant of SN1006

The appearance of the young supernova remnant SN1006 is dominated by emission from non-radiative shocks in the NE and NW regions. At X-ray energies the northeast shock exhibits predominantly nonthermal synchrotron emission, while the northwest shock exhibits a thermal spectrum. We present far ultraviolet spectra of the northeast (NE) and northwest (NW) portions of SN 1006 acquired with the Far Ultraviolet Spectroscopic Explorer (FUSE). We have detected emission lines of O VI (1032, 1038 Å) and broad Ly-β (1025 Å) in the NW filament, but detect no emission lines in the NE region down to a level of 4.7 × 10 erg cm s arcsecond. We observed in the NW an O VI intensity of 2.0 ± 0.2 × 10 erg cm s arcsecond and measured an O VI line width of 2100 ± 200 km s at a position where the Hα width was measured to be 2290 ± 80 km s (Ghavamian et al. 2002). This implies less than mass proportional heating of the ions. Using the ratio of intensities, I(NW)/I(NE)∼n(NW)/n(NE), the density ratio of the two regions is found to be ≥ 4, a value that is with the uncertainties of the ratio of 2.5 measured by Long et al. (2003). The derived O VI kinetic temperature is compared to previous estimates of electron, proton, and ion temperatures in the remnant to study the relative heating efficiency of various species at the shock front. The degree of postshock temperature equilibration may be crucial to particle acceleration since the temperature of each species determines the number of high speed particles available for injection into an acceleration process that could produce Galactic cosmic rays. Subject headings: ISM:individual(SN1006)–supernova remnants–shock waves– ultraviolet:ISM University of Michigan, Department Of Atmospheric, Oceanic and Space Sciences, 2455 Hayward, Ann Arbor MI 48109 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218-2686