发表机构
Korea Astronomy and Space Science Institute (KASI); Korea University of Science and Technology; Department of Astronomy, School of Science, The University of Tokyo; Department of Earth, Environment, and Physics, Worcester State University; Institut de Ciències de l’Espai (ICE-CSIC); Joint ALMA Observatory; National Radio Astronomy Observatory; Institute for Advanced Study, Kyushu University; Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University; School of Astronomy and Space Science, Nanjing University; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（韩国天文与空间科学研究所; 韩国科学技术院; 东京大学理学部天文学科; 伍斯特州立大学地球、环境与物理系; 太空科学学院（CSIC）; ALMA联合观测所; 美国国家射电天文台; 九州大学高等研究院; 九州大学理学地学行星科学系; 南京大学天文与空间科学学院; 教育部现代天文与天体物理重点实验室（南京大学））
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用ALMA观测NGC6334I的尘埃偏振，发现高光学深度与颗粒对齐效率降低可解释致密区低偏振度，还揭示磁场结构随密度的转变及颗粒生长、破坏的相关特征。
AI 中文摘要
大质量恒星的强辐射预计会通过辐射力矩（RATs）显著影响尘埃颗粒的对齐与演化。我们利用阿塔卡马大型毫米/亚毫米波阵列（ALMA）的1.2毫米尘埃连续谱偏振观测，在大质量恒星形成区NGC6334I中研究该效应。偏振度范围为≲1%至~10%，且随柱密度增加而降低；尽管致密核温度高达~100 K（预计RATs可实现高效颗粒对齐），其偏振度仍低于2%。我们研究了颗粒对齐、颗粒生长、颗粒破坏、磁场缠结及局地物理条件对MM1、MM2、MM3及其周边偏振特性的影响。偏振角弥散显示，磁场缠结在中等密度下会导致去偏振，但无法完全解释最低偏振度。通过基于RATs的颗粒对齐与偏振建模，我们发现对齐效率降低和高光学深度可重现最致密区域的低偏振度。MM2存在颗粒生长证据，最大颗粒尺寸a_max~0.35-1.0 μm；MM1的最大颗粒尺寸较小，为~0.35-0.50 μm；考虑光学深度后，MM1的推断颗粒尺寸增至~1.0-2.0 μm。对强爆发产生的辐射力矩破坏的分析估计表明，高温、中等密度区域的微米级颗粒可碎裂为亚微米级颗粒；即便存在微米级颗粒，高光学深度也可解释最致密区域的低偏振度。纳入磁场倾角效应后，显示从低密度下以天球平面场为主，转变为高密度下更倾向于视线方向的结构。
英文摘要
Intense radiation from high-mass stars is expected to significantly affect dust grain alignment and evolution through RAdiative Torques (RATs). We investigate this effect in a massive star-forming region, NGC6334I, using 1.2 mm dust continuum polarization observations from the Atacama Large Millimeter/submillimeter Array. The polarization fraction spans from $\lesssim1\%$ to $\sim10\%$ and decreases with increasing column density, remaining below $2\%$ in dense cores despite high temperatures ($\sim100$ K), where efficient grain alignment by RATs is expected. We investigate how grain alignment, grain growth, grain disruption, B-field tangling, and local physical conditions affect the polarization properties of MM1, MM2, MM3, and their surroundings. Polarization angle dispersion shows that B-field tangling contributes to depolarization at moderate densities but cannot fully explain the lowest polarization fractions. Using RAT-based grain alignment and polarization modeling, we find that reduced alignment efficiency and high optical depth reproduce the low polarization in the densest regions. MM2 shows evidence of grain growth, with maximum grain sizes $a_{\max}\sim0.35-1.0~μ$m, while MM1 exhibits smaller values of $\sim0.35-0.50~μ$m. Accounting for optical depth increases the inferred grain sizes in MM1 to $\sim1.0-2.0~μ$m. Analytical estimates of radiative torque disruption from the intense outburst suggest that micron-sized grains in high-temperature, moderate-density regions can fragment into submicron grains. Alternatively, high optical depth may also explain the low polarization in the densest regions even in the presence of micron-sized grains. Incorporating the B-field inclination effect indicates a transition from predominantly plane-of-sky fields at low densities to more line-of-sight-aligned configurations at high densities.
Comments35 pages, 29 figures, and 3 tables
