thE impaCt Of coSmic raYS on the inTerstEllar Medium

In recent years, there has been an increasing interest in the impact of cosmic rays (CRs) on the evolution of galaxies.

The fact that the local CR energy density is comparable to the turbulent and magnetic energy densities implies that CRs can potentially influence the dynamics of the interstellar medium (ISM), regulating the level of star formation and driving large-scale outflows.

Moreover, CRs have long been known to be a key source of heating and ionization in the dense ISM shielded from photoionizing radiation.

Despite the considerable progress made in the field, there are still uncertainties in modeling the galactic-scale transport of CRs.

As a result, the extent to which CRs impact ISM structure and evolution is yet unclear.ECOSYSTEM will provide a significant step forward in the field, thanks to state-of-the-art MHD simulations modeling the transport of spectrally resolved CRs and their interplay with the ambient gas, with unprecedented physical detail.

These simulations will employ a new algorithm in which the propagation of CRs depends on the properties of the multiphase ISM and CRs themselves.

To cover multiple ISM scales and conditions, the project will combine simulations of kpc-sized portions of galactic disks representative of galactic environments typical of Milky Way-like galaxies with zoom-in simulations of individual molecular clouds, and will explore different galactic properties in terms of star formation rate, gas surface density, and gravitational potential.This project will deliver a comprehensive theoretical investigation of how the distribution of CRs, in space and energy, vary with the dynamical, thermal, and magnetic properties of the gas.

Three questions will be addressed thanks to ECOSYSTEM: 1) What is the impact of CRs within the ISM disk and for galactic wind driving? 2) How do the large-scale spatial and spectral distribution of CRs depend on galactic environment? 3) What sets the CR ionization rate in the dense ISM?