The interstellar medium in young supernova remnants: key to the production of cosmic X-rays and $\gamma $-rays

We review recent progress in elucidating the relationship between high-energy radiation and interstellar medium (ISM) young supernova remnants (SNRs) with ages of $\sim$2000 yr, focusing particular on RX J1713.7$-$3946 RCW 86. Both SNRs emit strong nonthermal X-rays TeV $\gamma$-rays, they contain clumpy distributions gas that includes both atomic molecular hydrogen. find shock-cloud interactions provide a viable explanation for spatial correlation ISM. In these interactions, shocks hit typically pc-scale dense cores, generating highly turbulent velocity field amplifies magnetic up to 0.1-1 mG. This amplification leads enhanced synchrotron emission around clumps, whereas cosmic-ray electrons do not penetrate clumps. Accordingly, exhibit distribution similar ISM pc scale, while are anticorrelated at sub-pc scales. These results predict hadronic $\gamma$-rays can be emitted from resulting correspondence The current resolution $\gamma$-ray observations is too low resolve this correspondence. Future Cherenkov Telescope Array will able sub-pc-scale clues origin cosmic $\gamma$-rays.