DIFFUSE NONTHERMAL X-RAY EMISSION: EVIDENCE OF COSMIC-RAY ACCELERATION AT THE SHOCK FRONT IN IC 1262

摘要

We report the first localization of diffuse, nonthermal, X-ray emission from a nearby galaxy cluster. Using Chandra data, we have isolated a diffuse nonthermal X-ray component with a photon index of Γ_X = 2.21_(-0.15)~(+0.14) and a flux of 9.5_(-2.5)~(+1.1) x 10~(-5) photons cm~(-2) s~(-1) keV~(-1) at 1 keV that extends from ～1′.5 to ～2′.5 to the south of the X-ray flux peak. Comparison with simulations implies that the diffuse nonthermal emission is produced by primary electrons, accelerated at shocks to relativistic velocities. Using these results and the flux and hardness maps produced with data from the Chandra Advanced CCD Imaging Spectrometer, we conclude that a smaller subclump coming from the north merged with IC 1262. The offset of the cD galaxy from the X-ray peak and large peculiar velocity indicate that the subclump's impact parameter was to the west and on the near side of IC 1262.