Giada Peron (Italy)
peron @ mpi-hd.mpg.de
Cosmic Rays, Giant Molecular Clouds and Diffuse Gamma-Ray emission of the Galactic Disk
Cosmic Rays (CRs) have been discovered more than hundred years ago, but many aspects of their origin remain still unknown. Several experiments like PAMELA or AMS provided precise measurements of CRs in the Earth's neighborhood. However, for the understanding of the origin of CRs this information about the local CRs is not sufficient. Namely, one needs information about the fluxes and energy distributions of CRs all around the Galaxy. This can be done through the measurements of secondary products that originate as CRs interact with the interstellar medium (ISM). Here stands the crucial role of gamma-ray astrophysics: the main product of interactions of galactic CRs are high energy photons (up to ∼ 100 TeV), that can reach us undeflected from the entire Galaxy. The energy spectrum of these photons is proportional to the gas density and depends only on the process cross-sections. Therefore the gamma-ray emission traces the spatial and energy distributions of primary Cosmic Rays.
The aim of my PhD project is to study this gamma-ray radiation. I will focus on Molecular Clouds, that are small (10-100 pc) regions of cold matter (10-20 K). The number density of gas in these clouds (∼ 100-1000 cm−3 ) is higher at least by two orders of magnitude the average density of ISM. Thus, the rates of CR interactions, and correspondingly the gamma-ray emissivities are significantly enhanced in these clouds. The latest achievements of radio/mm surveys of MCs and the observations of these objects in high energy gamma-rays with the Fermi-LAT (Large Area Telescope) provide unique possibilities for exploration of CR properties throughout the Galaxy. This will constitute the core of my PhD thesis.
Supervisor: Felix Aharonian (MPIK)