Research
1.Observational studies of B fields in molecular clouds
Initial condition of low-mass and high-mass star formation (Liu et al. 2019,2020, and 2024)
In Liu et al. 2020 and 2024, I studied the the multi-scale B of the massive infrared dark cloud (IRDC) G28.34+0.06 (the Dragon cloud) with dust polarization data from ALMA, JCMT, and Planck. These two studies reveal the role of B fields at different scales in an individual early-stage massive star formation region.
在Liu et al. 2020和2024中，我利用ALMA、JCMT、Planck的数据研究了一个处于大质量恒星形成早期阶段的红外暗云G28.34+0.06(又称龙分子云)的多尺度磁场。
《來自星塵的暗龍》：黑暗之龍沉眠深紅星空，須彌微塵暗孕星火之原。打破吧，那磁場的鎖鏈；征服吧，那無序的湍流。光之意志自星骸中重生，藍白之星定閃耀銀河！ “Dark Dragon from Dust”: The dark dragon slumbers in the crimson sky, amidst the interstellar dust, harboring the origins of stellar fire. Breaking free from the chains of magnetic fields; conquering the chaotic turbulence. The will of light is reborn from the remnants of stars; the blue and white massive stars shall shine in the galaxy!
Left: Magnetic field orientations of the Dragon cloud G28.34+0.06 revealed by Planck (orange lines) and JCMT (white lines) overlaid on the Spitzer three-color image (red/green/blue = 8.0/4.5/3.6). Right: B of clump MM4 in G28.34 revealed by ALMA.
In Liu et al. 2019, I investigated the B field properties in the low-mass starless core Ophiuchus C (in early low-mass star formation) using dust polarization observations from JCMT.
在Liu et al. 2019中，我利用JCMT的观测数据研究了一个处于小质量恒星形成早期阶段的无星云核Ophiuchus C的磁场性质。
Multi-scale magnetic properties in nearby high-mass star-forming region NGC 6334 (Liu et al. 2023a)
Using dust polarization data from ALMA, JCMT, and Planck, I investigated the multi-scale (e.g., $\sim$10 pc clouds, $\sim$1 pc clumps, $\sim$0.1 pc cores, $\sim$0.01 pc condensations…) B field property in the nearby massive star formation region NGC 6334.
利用ALMA、JCMT、Planck的数据，我研究了邻近大质量恒星形成区NGC 6334的多尺度磁场。
Magnetic field orientations (line segments) overlaid on the dust emission map (colorscales) in NGC 6334 from Planck, JCMT, and ALMA.
2.Numerical study of analysis methods used to interpret B fields
Calibrating the DCF method with numerical simulations (Liu et al. 2021)
We conducted a numerical study using a series of 3D magnetohydrodynamic (MHD) and polarization radiative transfer simulations (made with RAMSES and POLARIS) of clustered star formation regions with different magnetic and turbulent levels, aiming at investigating the uncertainty of the DCF method at sub-parsec scales (i.e., dense clumps/cores) that are associated with significant self-gravity.
利用具有不同磁场强度和湍动强度的成团恒星形成区的三维磁流体力学和偏振辐射转移数值模拟，我们对测量磁场强度最常用的DCF统计方法在强引力高密度环境下的准确性进行了研究。
Examples of the synthetic observation of our simulations. Line integral convolution map shows the magnetic field orientation. Colorscales indicate the dust emission.
3.Review of B field studies in the literature
A Compilation of All the DCF Estimations (Liu et al. 2022a)
I collected all the DCF estimations of B strength from polarized dust emission observations in the literature (230 estimations from 75 papers) and corrected them with numerical results (Liu et al. 2021). The statistical study systematically reveals the general property of B fields in star formation regions, which is instructive for the future development of star formation theories.
我整理收集了所有历史文献里利用DCF方法测量的恒星形成区的磁场强度，并系统性地研究了磁场的一般统计性质。
Normalized mass-to-flux ratio (gravitational-to-magnetic ratio) as a function of gas column density.
A review of statistical methods used to study magnetic field properties (Liu et al. 2022b)
We have recently reviewed the advances and limitations of several analysis methods of magnetic fields and summarized their applications to observations. For instance, the Davis-Chandrasekhar-Fermi (DCF) method (Davis & Greenstein, 1951, Chandrasekhar & Fermi, 1953 ), the polarization-intensity gradient (KTH) method (Koch et al., 2012), and the Histogram of Relative Orientations (HRO) analysis (Soler et al., 2013).
我们撰写了一篇有关分子云磁场研究使用最广泛的三种统计分析方法(DCF、HRO、KTH方法)的综述文章。