Possible Evidence for Cosmic-Ray Acceleration in the Type Ia SNR RCW 86: Spatial Correlation between TeV Gamma-Rays and Interstellar Atomic Protons

REYNOSO, E. M.; NAGAYA, T.; TORII, K.; INOUE, T.; TACHIHARA, K.; ROWELL, G.; YAMANE, Y.; HAYASHI, K.; MITSUISHI, I.; YAMAMOTO, H.; SANO, H.; JUNG-RICHARDT, I.; YOSHIIKE, S.; MAXTED, N.; INUTSUKA, S.; FUKUI, Y.

The Astrophysical Journal

IOP Publishing

Año: 2019 vol. 876 p. 37 - 49

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 predominantly 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 μG. 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 contribute alongside the 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.