Possible Evidence for Cosmic-Ray Acceleration in the Type Ia SNR RCW 86:
  Spatial Correlation between TeV Gamma rays and Interstellar Atomic Protons
  We present a detailed morphological study of TeV gamma rays, synchrotron
radiation, and interstellar gas in the young Type Ia supernova remnant (SNR)
RCW 86. We find that the interstellar atomic gas shows good spatial correlation
with the gamma rays, indicating that the TeV gamma rays from RCW 86 are likely
to be dominantly of hadronic origin. In contrast, the spatial correlation
between the interstellar molecular cloud and the TeV gamma rays is poor in the
southeastern shell of the SNR. We argue that this poor correlation can be
attributed to the low-energy cosmic rays (~ 1 TeV) not penetrating into the
dense molecular cloud due to an enhancement of the turbulent magnetic field
around the dense cloud of ~ 10-100 $\mu$G. We also find that the southwestern
shell, which is bright in both synchrotron X-ray and radio continuum radiation,
shows a significant gamma-ray excess compared with the interstellar proton
column density, suggesting that leptonic gamma rays via inverse Compton
scattering possibly contributes along with hadronic gamma rays. The total
cosmic-ray energies of the young TeV gamma-ray SNRs$-$RX J1713.7$-$3946, Vela
Jr, HESS J1731$-$347, and RCW 86$-$are roughly similar, which indicates that
cosmic rays can be accelerated in both the core-collapse and Type Ia
supernovae. The total energy of cosmic rays derived using the gas density, ~
10$^{48}$-10$^{49}$ erg, gives a safe lower limit due mainly to the low filling
factor of interstellar gas within the shell.
