Ongoing


Formation of globular clusters (GCs) in local group satellite galaxies
We make modifications to the Chen & Gnedin (2022) model so that we can apply the model to satellite galaxies in N-body simulations.

Modelling the kinematics of GCs
The advent of the Gaia mission has enabled detailed kinematics studies of the Galactic GCs and revolutionized our understanding of the connections between GC properties and galaxy assembly. We update the GC formation model developed by Choksi & Gnedin (2019) by assigning GCs to particles in the Illustris TNG simulation based on age and location. This adds spatial and kinematic information to the modeled GCs. The model successfully reproduces the radial distribution and various kinematic properties of the Galactic GCs. We also analyze GCs from different origins: In outer galaxy, ex-situ clusters are more dominant than the clusters formed in-situ, which explains the gradient of GC metallicity. See our first paper (Chen & Gnedin 2022) for details.

Radial profile of GCs Radial profile of GCs split by in-situ/ex-situ

Radial profiles of all modelled GCs (left) and split by in-situ/ex-situ (right).

Giant molecular clouds (GMCs) with different initial density profiles
Together with Hui Li and Mark Vogelsberger, I perform a suite of simulations to investigate the effects of initial density profiles on the evolution of star clusters in GMCs. We find that the uniform profile follows a "hierarchical" cluster formation mode, while the steep power-law profiles show an "accretion" dominated mode. These two cluster formation modes lead to different proprieties of the most massive clusters in GMCs. See our first paper (Chen, Li, & Vogelsberger 2021) for details.

Projection of hierarchical cluster formation mode Projection of concentrated cluster formation mode

"Hierarchical" (left) and "accretion" (right) modes for cluster formation.



Previous


Pre-burst stage of gamma-ray bursts (GRBs)
Based on the cosmic light speed variation, I found a novel pre-burst stage for GRBs. I also employed a primary clustering method of machine learning to classify this stage with the data from the Fermi telescope. The work was completed in late 2019 but was accepted for publication in 2021 due to the COVID-19 pandemic (see, Chen and Ma 2021).

Two classifications of GRB photons

Two classifications of GRB photons. Classification A distinguishes pre-burst from main-burst.


Contact


Email
ybchen (at) umich.edu

Adress
323 West Hall, 1085 S. University, Ann Arbor, MI 48109-1107, USA

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© 2020-2023 Bill Chen.
Last Modified in January 2023.