学术报告—New Frontiers of Dark Matter Halo

Abstract:

Current theoretical understandings of the nonlinear structure formation and galaxy formation processes are largely built upon a central concept that dark matter in the Universe are mostly contained in virialized clumps called dark matter halos, with the boundary of a halo described by its virial radius. However, the growth of a halo means it is inevitably surrounded by a non-virialized envelope of freshly accreted material. Failing to account for this envelope has led to major difficulties in the classical halo model, while a number of recent works have attempted to solve the problems by redefining the halo with new boundaries.

In this talk I will report our recent development of the depletion radius, which is a new but fundamental halo boundary stemming from the macroscopic physics of halo growth. I will show that the depletion radius is both an important physical probe of halo evolution and a concise geometric boundary for halo models of the large scale structure, capable of overcoming major limitations of the classical halo in a systematic way. I will also present our observational measurements of the depletion radius for both our Milky Way halo and DESI galaxy groups.

Bio:

Jiaxin Han is an associate professor at Shanghai Jiao Tong University. He graduated from Nanjing University in 2007,  and got his PhD from Shanghai Astronomical Observatory in 2013, with half of his PhD time spent at Durham University. After that he worked as a postdoc at the Institute for Computational Cosmology (Durham University, UK) and Kavli IPMU(Tokyo University, Japan), before joining Shanghai Jiao Tong University in 2018. His research focuses on computational and observational studies of the dark matter distribution in the Universe especially on halo and subhalo scale, using various techniques including numerical simulation, dynamical modelling, gravitational lensing and indirect detection. He is also leading recent cosmological simulation efforts (the Jiutian simulations) for the Chinese space station telescope. He has been supported by the Marie-Curie foundation (EU), JSPS (Japan) and the national talent recruitment program (China), among others.