The origin of galaxies

Advisor: Pavel Kroupa (AI MFF CUNI and University of Bonn)

Funding: Top-up funding may be available.

Website: https://astro.uni-bonn.de/~pavel/

The current standard model of cosmology (the SMoC) is subject to significant conflict with data. Examples amongst many are the Hubble tension and planes of satellites problems. The recent analysis of the matter distribution on a Gpc scale and of the Hubble tension by our team in Bonn (Haslbauer et al., 2020) shows the SMoC to be falsified at the seven sigma confidence level while the data are well consistent with the Universe being Milgromian rather than Einsteinian/Newtonian (note that physical theories count as being entirely and robustly ruled out when the tests reach a confidence level of 5 sigma).

The detection with more than five sigma confidence of the breaking of the strong equivalence principle on galactic scales which negates Einsteinian/Newtonian gravitation as being relevant for galactic and cosmological astrophysics verifies a major prediction of the Milgromian gravitational theory (Chae et al. 2020). This prediction constitutes an entirely new dynamical phenomenon not known in Newtonian or Einsteinian gravitation and is called the external field effect (EFE). The EFE leads to structure growth on cosmological scales to be self-constrained (Haslbauer et al. 2020).

Galaxy formation in Milgromian dynamics solves a number of major hitherto unsolved problems (Wittenburg et al. 2020) by explaining why the very vast majority of galaxies are rotationally supported disk galaxies and why they have exponential profiles, as well as why they have flat rotation curves and why they follow baryonic Tully-Fisher relation and the radial acceleration relation. A current project at Charles University lead by Robin Eappen and in this group is studying the formation of elliptical galaxies.

Given these very exciting developments, this project will contain cosmological simulations in order to quantify the structures which develop self-consistently and which types of galaxies form and evolve in a Milgromian Universe. To achieve this goal and in the collaborative network involving the Universities of Bonn and Strasbourg, the Milgromian cosmological code developed in Bonn will be ported to a supercomputer. Problems to study will be the time-dependent dispersion of matter density in adjacent regions, the types of galaxies that emerge and the satellite galaxy population in order to address some of the recent observational challenges.

Description of figure: The redshift=0 snapshot of the first-ever simulation of a Universe which is born in a BigBang but made only of normal matter. The simulation was performed by Nils Wittenburg and Indranil Banik at Bonn Universe and is being prepared for publication. It was made with the Phantom of Ramses adaptive mesh refinement code developed in Bonn in collaboration with Strasbourg (Lueghausen et al. 2015) and shows for the first time how rotationally supported disk galaxies emerge in large numbers along gas filaments which evolve in the expanding and cooling Universe.