Dark matter halos are approximately virialized condensation of dark matter and serve as the building blocks of large scale structure and galaxy formation. These structures, however, are not fully in equilibrium and contain large amounts of substructures including subhalos and streams. Robust identification and analytical understanding of the properties and distributions of these substructrures play important roles for both galaxy formation modelling and dark matter observations. In this talk I will first introduce our unique approach of subhalo identification in numerical simulations, followed by an analytical model for the mass and spatial distribution of subhalos in the framework of hierarchical structure formation. The results are then confronted with observations including gravitational lensing measurements of subhalos and indirect dark matter detection in gamma-rays. Aside from the existence of subhalos, the apparently smooth part of the halo is not in full equilibrium either, and bears imprints of its hierarchical formation history. Deviation from steady-state leads to systematic biases when tracer dynamics are used to model the underlying halo potential, with different tracers showing different bias levels. For the modelling of the outer halo, I will show that satellite galaxies exhibit smaller systematic biases than halo stars. Such systematic biases can be further reduced by going beyond the steady-state assumption. Using a sample of satellite galaxies with updated phase-space coordinates from GAIA data, we are able to measure the halo mass of the MW to an unprecedented accuracy.
BIO
Jiaxin Han got his PhD from Shanghai Astronomical Observatory in 2013 and subsequently worked as postdocs at the Institute for Computational Cosmology (Durham University, UK) and the Kavli Institute for the Physics and Mathematics of the Universe (IPMU, Tokyo University), before joining Shanghai Jiao Tong University in 2018 as a tenure-track associate professor. His research is focused on astrophysical studies of the property and distribution of dark matter through various theoretical and observational approaches. He has been supported by the Marie-Curie grant (EU), the JSPS grant (Japan), the national recruitment grant (China) and the NSFC grant.
Host: Zheng Cai
