F5 : CRISMI – The Cosmic-Ray InterStellar-Medium Interplay
Cosmic rays can play an important dynamical role in the evolution of their host galaxy by modifying the gas cycles and magnetic fields, but we know too little about their transport in different types of interstellar environments to model their impact. The project aims to constrain the different transport modes by using for the first time complementary simulations and observations. We therefore propose to develop state-of-the-art simulations of the coupled evolution of interstellar clouds and cosmic rays and to compare them with radio and gamma-ray observations of comparable regions in the Milky Way.
Are cosmic rays actors or passengers in galaxy evolution? In the current models of galaxy evolution stars form too efficiently and too early in the history of the Universe. High-energy processes such as jets from supermassive black holes and supernova explosions can modify how the gas and magnetic fields cycle in and out of a galaxy, but their impact fails to explain key observations such as galactic outflows.
Cosmic rays can play a particular role in galaxy evolution as they mediate energy transfers from supernovae to the interstellar medium over thousands of parsecs and tens of millions of years around their source. They also increase the gas buoyancy and add anisotropic pressures along magnetic field lines and off galactic discs.
To evaluate their impact, it is central to understand how cosmic rays propagate through a galaxy and how their transport properties vary with the ambient interstellar conditions. To gain insight into this problem, we propose to compare for the first time the distribution of cosmic rays obtained in numerical simulations of interstellar clouds with measurements obtained from multi-wavelength observations in comparable regions of the Milky Way.
A team of well-known experts in the Astrophysics Department will advise the PhD student on high-performance computing simulations and on multitracer observations of the interstellar medium, magnetic topology, and cosmic rays. He or she will also work within the broad international collaboration for the Fermi Gamma-ray Space Telescope.