【直播】【中国科大寰宇开物天文讲坛】Evolution of Dark Matter Halo Structure...
Evolution of Dark Matter Halo Structure & Constraints on Galaxy Assembly Bias
2021年11月30日 10:00
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报告人：
Kuan Wang | University of Michigan, Ann Arbor）
主办方：
中国科学技术大学 - 天文学系
报告摘要
In the concordance model of modern cosmology, dark matter is five times as abundant as the ordinary baryonic matter. While its nature remains one of the most challenging questions in today’s physics, dark matter has been established as a defining factor in the large scale structure we observe. Visible galaxies form in the potential wells of dark matter density peaks, known as halos. Empirical galaxy–halo connection models, which reconstruct the observable components of the Universe from our theoretical knowledge of the dark sector, are broadly used for their simplicity and effectiveness. The fundamental premise of such empirical models is the statistical dependence of galaxy properties on halo properties, the latter of which are easily accessible through gravitational N-body simulations.
With tremendous amounts of observational data being produced by new generations of surveys, theoretical tools need also be further developed to exploit the full potential of data. In particular, observables on small, non-linear scales are a promising source of statistical information for constraining both cosmology and galaxy physics. These observables require detailed knowledge of dark matter halos, which are the basic units of non-linear structure, and a connection between galaxies and halos. Improving the modeling of halos and their connection to galaxies is therefore an urgent and important task in the new era of precision cosmology.
We aim to improve our understanding of the evolution of dark matter halos and the statistical dependence of galaxy properties on the properties of halos in which they reside. First, we investigate how the present-day halo structure emerges from the halo mass assembly history, and characterize the respective contribution from the two modes of halo assembly: pseudo-evolution and physical merger events. We uncover the significant impact of mergers on the evolution of halo structure, and recognize universal patterns in merger events. These findings will also shed light on the galaxy evolution in halos. In the second part, we test the validity of the simplifying assumptions adopted in galaxy–halo connection models. We identify the optimal combination of observable statistics –– galaxy count statistics in addition to the traditionally used two point function –– that contain the most information on the galaxy–halo connection, and obtain observational constraints on the model using these statistics. For some galaxy samples, we observationally confirm that the inclusion of galaxy count statistics significantly improves the constraining power, and find definitive evidence for galaxy assembly bias, the dependence of the galaxy–halo connection on secondary halo properties besides mass. These results inform the physics of galaxy formation and evolution and cosmological inferences.
报告人介绍
Kuan Wang is a data oriented theoretical cosmologist. She obtained her bachelor's degree in astronomy at the University of Science and Technology of China in 2015, and earned her PhD from the University of Pittsburgh in 2021. Kuan is now a Leinweber Postdoctoral Research Fellow in the Department of Physics at the University of Michigan, Ann Arbor. Her research interests include galaxy–halo connection, cosmological probes from galaxy surveys, and cosmological simulations.
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