Gamma-Rays and Cosmic-Rays from SNRs: Challenges and the Future

Hadronic cosmic rays accelerated up to 10-100 GeV have been finally associated with a class of middle-aged SNRs and possibly young ones. We will review the recent AGILE and Fermi-LAT results on SNRs with particular emphasis on the difficult task of distinguishing leptonic and hadronic gamma-ray emission. Current data are surprising and challenging theoretical models based on non-linear diffusive acceleration processes. Different environments and conditions surrounding SNR shocks appear not to influence the GeV part of the spectrum that shows a universal slope near 2.3. We will discuss the implications of this result that seems to be valid for both young and middle-aged SNRs. The SNR shock morphologies and high-energy emission can be very complex. We definitely need better angular resolution and sensitivities to resolve SNR morphologies and surrounding ISM in gamma-rays, a task that can be crucial for future observatories and space missions. Solving the problem of the origin of Galactic cosmic rays turns out to be much more complex than anticipated a few years ago. Additional efforts are needed both theoretically and observationally , the future may be bright.