Seminar by Dr. Philipp Girichidis, University of Heidelberg

Abstract

Cosmic rays (CRs) are high-energy particles with an energy density comparable to that of other components in the interstellar medium (ISM) and with very distinct cooling and transport processes.
The low cooling efficiency of CRs allows them to travel long distances from their point of acceleration. As a result, they influence star formation on small scales and at high densities.
Furthermore, the pressure exerted by CRs permeates the galaxy, enabling the launch of galactic-scale outflows. These outflows have a significant influence on galactic evolution.

In this review, I will focus on the dynamical impact of CRs, demonstrating how they shape the ISM and contribute to the launch of galactic outflows.
There are significant uncertainties in our understanding of CR astrophysics, particularly regarding the speed at which they are transported and the efficiency with which they lose energy.
I will highlight efforts to address these uncertainties by incorporating CRs into hydrodynamic simulations.
These simulations aim to accurately model their evolution from non-relativistic to relativistic regimes, while also accounting for the full magnetohydrodynamic evolution.
By doing so, this improves the accuracy of the CR-driven dynamics and allows us to generate synthetic observables such as gamma rays and synchrotron radiation, which provide valuable insights into the transport and cooling properties of CRs.