Title: Reverse Engineering: Inferring Primordial Dark Matter Halos from Observations

 

Speaker: Pengfei Li (Assistant Professor)

Affiliation: Nanjing University

 

Abstract: Cold dark matter (CDM)-only simulations made clear predictions on the density profile of primordial dark matter halos. As baryons fall into their centers and form galaxies, primordial dark matter halos can evolve significantly and thereby differ from current ones. By numerically calculating the halo evolution due to baryonic compression, we found that the CDM halos of massive galaxies inevitably become super cuspy, consistent with TNG simulations. As such, Baryonic compression dominates over feedback in massive galaxies. We developed a new approach to reverse engineer the primordial dark matter halos for observed galaxies. Using the latest rotation curve from Gaia, we found the Milky Way has an odd halo structure: it presents a large core in the center and a steep decline in the outskirt. Therefore, massive galaxies suffer a similar cusp-core problem as dwarf galaxies do, which is yet to be explained in the CDM paradigm. These demonstrate that numerical calculation is a prospective approach to study the evolution of dark matter halos.

 

Bio: Dr. Pengfei Li is currently an assistant professor in Nanjing University. He got his PhD in Astronomy from Case Western Reserve University (USA) in 2020, a Master in Theoretical High-Energy Physics from Peking University in 2015, and a Bachelor in Engineering from Huazhong University of Science and Technology in 2012. He was an Alexander von Humboldt fellow at Leibniz-Institute for Astrophysics (Germany) from 2021 to 2024. He has been using galaxies and galaxy clusters to test dark matter models and the theory of gravity.