Periodic Reporting for period 2 - COMPLEX (Cosmological magnetic fields and plasma physics in extended structures)
Reporting period: 2022-07-01 to 2023-12-31
Within the framework of the so-called ΛCDM cosmological model, structures form in a hierarchical bottom-up fashion. Understanding how galaxies and galaxy clusters form in this scenario requires a proper description of the complex physical processes that determine the evolution of the cosmic baryons, which fall into the potential wells of the underlying dark matter, cool, and finally condense to form stars. In turn, these processes affect the observable properties of the intergalactic and intracluster media (IGM and ICM) through the action of various feedback processes: gas and metals synthesized by stars are blown out by galactic winds and other gas dynamical processes, and mix with the surrounding IGM/ICM. Furthermore, gas accretion onto supermassive black holes also generates feedback onto the surrounding medium, which has to be consistently coupled with the (magneto-)hydrodynamics. However, a detailed understanding of the underlying physical processes is still extremely limited, as they are currently built on “ad hoc”, empirically constructed sub-grid models. Additional physical processes like magnetic fields and cosmic rays are only rarely and in a very simplified manner included within such models, and typically not self consistently coupled to the other processes. Furthermore, it is even not clear if descriptions of the fluid following Spitzer/Braginsky formulations are adequate (e.g. waves vs. collisions for defining plasma properties).
Here, the "COMPLEX" project is aimed at refining our understanding of the most important physical processes shaping formation and evolution of the cosmic large scale structure, as well as the galaxies and galaxy clusters within them. COMPLEX will focus on the self consistent treatment of fluid properties which describe turbulence, the mixing and the transport processes within the gas, together with its additional components like magnetic fields and so called cosmic rays.
This will boost the insight into the elementary processes defining the fluid properties of the visible matter in the universe and therefore advance our understanding of the evolution of galaxies and galaxy clusters to the next level needed to interpret forthcoming astronomical surveys. Therefor it will contribute to our understanding of the Universe in which we life and give new insights in how the large scale structures and the embedded galaxies within our Universe form and evolve.
Here, the "COMPLEX" project is aimed at refining our understanding of the most important physical processes shaping formation and evolution of the cosmic large scale structure, as well as the galaxies and galaxy clusters within them. COMPLEX will focus on the self consistent treatment of fluid properties which describe turbulence, the mixing and the transport processes within the gas, together with its additional components like magnetic fields and so called cosmic rays.
This will boost the insight into the elementary processes defining the fluid properties of the visible matter in the universe and therefore advance our understanding of the evolution of galaxies and galaxy clusters to the next level needed to interpret forthcoming astronomical surveys. Therefor it will contribute to our understanding of the Universe in which we life and give new insights in how the large scale structures and the embedded galaxies within our Universe form and evolve.
Cosmic rays and magnetic fields play a significant role for star formation driven outflows from galaxies as well as in depositing the energy output of super massive black holes in massive galaxies, galaxy clusters and the large scale structure of the Universe. Although they are therefore essential to understand the life-cycles of these cosmological structures, in practice their effects are typically buried within very simplified, effective phenomenological models.
We have been developing new and innovative models in form of updated, hydro-dynamical solvers for our cosmological simulations, as well as extending the hydro-dynamical treatment to include Spitzer like viscosity. We also developed the numerical tools to properly capture the treatment of cosmic ray electrons and protons in a spectral fashion.
Additional, general Improvement and optimizations in the overall numerical tools allowed us for the first time to cover a large enough dynamical range in the simulations that allowed us for the first time to resolve the relevant dissipation scales. Here we for the first time performed a galaxy cluster simulations where the spacial resolution of the simulation was more than the mean free path of the plasma within the relevant parts of the simulated galaxy cluster, which resembles a so far unprecedented simulation of a galaxy cluster. We also have been able first time to perform a cosmological simulation with a self consistent treatment of spectral cosmic rays.
These beyond state of the art simulations have allowed us to study the amplification process of magnetic fields within galaxy clusters as well as the evolution of cosmic rays within the large scale structures in unmatched detail.
We have been developing new and innovative models in form of updated, hydro-dynamical solvers for our cosmological simulations, as well as extending the hydro-dynamical treatment to include Spitzer like viscosity. We also developed the numerical tools to properly capture the treatment of cosmic ray electrons and protons in a spectral fashion.
Additional, general Improvement and optimizations in the overall numerical tools allowed us for the first time to cover a large enough dynamical range in the simulations that allowed us for the first time to resolve the relevant dissipation scales. Here we for the first time performed a galaxy cluster simulations where the spacial resolution of the simulation was more than the mean free path of the plasma within the relevant parts of the simulated galaxy cluster, which resembles a so far unprecedented simulation of a galaxy cluster. We also have been able first time to perform a cosmological simulation with a self consistent treatment of spectral cosmic rays.
These beyond state of the art simulations have allowed us to study the amplification process of magnetic fields within galaxy clusters as well as the evolution of cosmic rays within the large scale structures in unmatched detail.
Odd Radio Circles (ORCs) are a newly discovered class of radio sources, showing large scale, ring-like diffuse radio emission with a diameter of hundreds of kpc, around central, elliptical galaxies, without any detected counterparts at non-radio wavelength. The origin of these radio phenomena so far is not known. Galaxy formation simulations performed within COMPLEX revealed a so far overlooked, possible formation scenario. Similar to what is observed as radio relics in galaxy clusters, we discovered the possibility that these are merger-driven shocks, propagating away into the outer circum-galactic and intergalactic medium.
Based on these predictions and a freshly discovered object with radio shells located much closer to us than all the the previously found objects of this class, we where able to prove the presence of the gas around the galaxy hosting this radio phenomena based on x-ray observations. This marks the first time that diffuse emission beyond the radio waveband was detected for an ORC bringing us a gigantic step forward in understanding the formation mechanism of this observed radio phenomena.
Based on these predictions and a freshly discovered object with radio shells located much closer to us than all the the previously found objects of this class, we where able to prove the presence of the gas around the galaxy hosting this radio phenomena based on x-ray observations. This marks the first time that diffuse emission beyond the radio waveband was detected for an ORC bringing us a gigantic step forward in understanding the formation mechanism of this observed radio phenomena.