星系合併對於星系演化是至關重要的過程，藉由階層式結構形成模型，星系的結構得以與宇宙學的理論連結，並且解釋碰撞星系能歷顯著的成長期，而星系中的超大質量黑洞也會同時演化，然而，合併事件往往需數億年來完成，我們無法觀測任意事件的完整細部過程，所以唯一能研究星系合併從開始到結束的物理細節是藉由數值模擬的方式；我們在美國國家科學研究計算中心的超級電腦上使用流體模擬程式--小精靈(GIZMO)進行模擬，它被認為可以適當地替複雜的星系交互作用與超大質量黑洞成長建立模型，其中模擬星系的物理參數來自觀測的結果（例如：蓋亞任務、阿塔卡瑪大型毫米及次毫米波陣列），利用如此的模擬並考慮不同的星系相關物理機制，我們可以研討超大質量黑洞與其宿主星系性質（像是核球、恆星形成率與氣體分佈等等）的共同演化。

Galaxy mergers are crucial processes in galaxy evolution. They hold the key to connect the galactic structure to cosmology through the hierarchical structure formation, which explains that galaxy pairs undergoing a significant transitional stage, and the supermassive black holes (SMBHs) in the galaxies also evolve simultaneously. However, we cannot observe the entire process of any merger events, which take longer than a few billion years, so the only way to study the physics of galaxy mergers from beginning to the end is by utilizing numerical simulations. The hydrodynamics simulation code we used is called GIZMO, which is appropriate to model the processes of the complicated galaxy interactions and SMBH growth. We simulated galaxies with physical parameters based on the observational results (e.g. Gaia, ALMA) and run our simulations on powerful supercomputers at the National Energy Research Scientific Computing Center (NERSC) in the USA. By performing a suite of simulations with different physical conditions, we can investigate the co-evolution between SMBHs and their host galaxies for some properties such as bulge, star formation rate, gas distribution, and so on.

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