Galactic Gas Distribution and Cosmic-Ray Transport

• Applicants: Privatdozent Dr. Torsten Enßlin; Professor Dr. Philipp Mertsch
• Subject Area: Astrophysics and Astronomy
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495252601

The interstellar medium of the Milky Way shows complex interactions of gas, dust, magnetic fields, starlight, and cosmic rays (CRs). Transport and interactions of CRs are closely related. They are further influenced by the spatial distribution of CR sources, galactic gas, starlight, and magnetic fields. Reconstructing the 3D structure of each of these quantities would be a major advance in Galactic astrophysics and would also help to better determine the others from measured data. We propose a series of Galactic 3D reconstructions with successively increasing complexity, of CR density, its source density, gas density, gas velocity, and other related quantities. For this purpose, we extend existing approaches to gas tomography (GIFT) and dust tomography based on numerical methods of information field theory (NIFTy). To reconstruct the source density, we will integrate the PICARD transport code into our NIFTy inference machinery. The science products of this project will be made publicly available and will enable a number of follow-up studies, such as 3D modelling of the Galactic magnetic field. In addition to the 3D maps, we will publish associated uncertainty maps and statistical summaries. Our goal is to greatly improve the simulation of transport and interaction of CRs also for the purpose of more accurately identifying their sources. The tomography methodology developed in this effort, which includes calculations of radiation transport, should also be useful for other fields, such as optical-acoustic medical imaging. To meet the challenges of this endeavour, we will combine our respective expert knowledge, which includes CR phenomenology, Bayesian inference, and numerical techniques.

• DFG Programme: Research Grants
• International Connection: Austria, Italy
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partners: Dr. Carmelo Evoli, Ph.D.; Dr. Philipp Gschwandtner; Professor Dr. Ralf Kissmann