12-20 July 2017
Asia/Seoul timezone
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BEXCO - Room F(201/202/203/204)

[CRI009] Cosmic-ray interaction in dense molecular clouds nearby SNR


  • Silvia CELLI

Primary authors


The presence of dense molecular clouds in the close vicinity of an astrophysical accelerator as a supernova remnant (SNR) affects the spectrum of accelerated particles, modifying the expected f(E)=E^{-2} behavior as derived in the diffusive shock acceleration scenario. Indeed, when a shock passes through a dense medium, magnetic field amplification is realized because of the turbulent motion of plasma around this medium (Rayleigh-Taylor instability): we therefore simulate the case of a diffusion coefficient at the cloud boundary much lower than that in the interstellar medium (ISM), solving the two-dimensional time-dependent transport equation for protons. Non homogeneous diffusion, advection in a shock flow and a constant injection term are included in the simulation. Our result show that high-energy cosmic-rays are able to penetrate these clouds earlier than low-energy ones: they are then gradually released in the ISM, while only at later times low-energy particles can penetrate the cloud too. The non-thermal emission from the accelerator, as that of gamma-rays produced in pp interactions, is directly affected by this phenomenon, given that such an emission is the result of CRs that effectively penetrate the clouds. Because of the presence of the cloud, the spectrum shows an hardening at low-energies. Moreover, the emission is time-dependent: the spectral break moves to lower energies as time passes by. Different thermodynamical properties of the background plasma are investigated and their effect on gamma-ray spectra are derived.