Cosmic Rays and Cosmology


Contact : Yohan Dubois, Stefano Gabici, Alexandre Marcowith

The workshop aims at considering the effect cosmic rays in the formation of large scale structures and in cosmology.
The main objectives of this workshop are twofold: 1) propose an overview of the role of cosmic ray in cosmology and in the galaxy formation process 2) gather specialists of different disciplines at the intersect of three program PNCG, PNHE and PCMI.

Cosmic rays, i.e. energetic subatomic particles mainly composed of protons have been discovered since more than one hundred years and have driven a large part of modern physics like Particle Physics and Astrophysics. The process of Cosmic Ray acceleration is likely connected with the death of massive stars which end their life as supernovae. However, collective interaction of massive star winds may also contribute to accelerate these particles up to high energies. Cosmic Rays energy cover nearly fifteen orders in magnitude. At the extreme multi-Exa eV particles are produced in extragalactic sources, which will be partly discussed in this workshop. The anisotropy of the Cosmic Ray flux at these energy is important to trace the topology of inter-galactic but also galactic magnetic fields. At lower energy, in the GeV-multi TeV range Cosmic Rays are important as gas and magnetic field tracers, as well as Cosmic Ray electrons for the magnetic field. GeV Cosmic Rays do also carry an important pressure that is the source of gas motion, in that way Cosmic rays can have some important impact over gas dynamics and hence over the star formation rate in our Galaxy. In effect, GeV Cosmic Rays are able to trigger their own turbulence via different type of instabilities, among which the most well- known is the streaming instability. These winds carry matter from the galactic disk, such matter being not available to produce new stars. Finally, in the MeV-GeV Cosmic Rays are an important source heavy nuclei spallation and gas ionization. MeV Cosmic Rays are able to ionize matter at high density columns where U.V. and X-ray photons can not penetrate. In that sense Cosmic Rays contribute to regulate gas-magnetic field coupling in the molecular cloud collapse process. If the Cosmic Ray properties of our Galaxy is reasonably constrained apart for the highest energies very few is known about the Cosmic Ray contents in the earlier stages of the Universe. But these particles should be there as soon as the first stars appeared and died. In this workshop we will discuss four main themes at the intersect of three different national programs that appeared in the literature in the recent years: 1) Cosmic Ray and primordial H2 ionization (PCMI) 2) Cosmic Rays and Pop III stars (PNCG) 3) Cosmic Ray and large scale structures dynamics (PNCG, PCMI) 4) Cosmic Ray content in galaxy clusters, link to UHECRs (PNHE). We will invite one renewed colleague to give a review on themes 3 and 4.

2 pm : Review on Cosmic Rays and Galaxy clusters
2.40 pm Contribution
3 pm Contribution
3.20 pm Contribution
3.40 pause
4 pm Review on Cosmic rays and large scale dynamics
4.40 pm Contribution
5 pm Contribution
5.20 Contribution
5.40 pm: end of the workshop