标题： EVN观测大质量恒星形成区中6.7 GHz甲醇脉泽偏振第四部分。 7个额外源的磁场强度限制和结构 显示英文标题

标题： EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions IV. Magnetic field strength limits and structure for 7 additional sources

摘要： 磁流体动力学模拟显示，在大质量原恒星形成过程中，磁场可以驱动分子外流。观测测量在10-100天文单位尺度上磁场的形态和强度的最佳探针是脉泽偏振。我们测量了大质量恒星形成区域周围在脉泽分辨率下磁场的方向，以确定磁场方向与外流方向之间是否存在关系。此外，通过估计磁場強度通過塞曼分裂測量，研究了磁場在大質量恒星形成區域動力學中的作用。我們選擇了一個通量限制樣本的31個大質量恒星形成區域，對磁場特性與分子外流特徵進行統計分析。我們報告了總樣本中七個大質量恒星形成區域的6.7 GHz CH3OH脈澤的線性和圓偏振發射，使用EVN。這些源是：G23.44-0.18，G25.83-0.18，G25.71-0.04，G28.31-0.39，G28.83-0.25，G29.96-0.02，以及G43.80-0.13。我們識別出總共219個CH3OH脈澤特徵，其中47個和2個分別顯示線性和圓偏振發射。我們測量了所有大質量YSO周圍有序的線性偏振矢量以及G25.71-0.04和G28.83-0.25的塞曼分裂。由於最近的理論結果，我們能夠根據我們的塞曼分裂測量提供磁場強度的下限。我們進一步確認（基於總通量限制樣本的約80%）在10-100天文單位尺度上的磁場優先沿著外流軸方向。估計的磁場強度|B_{||}|>61 mG和>21 mG分別朝向G25.71-0.04和G28.83-0.2，表明它在兩個區域的氣體動力學中占主導地位。 显示英文摘要

摘要： MHD simulations show that the magnetic field can drive molecular outflows during the formation of massive protostars. The best probe to observationally measure both the morphology and the strength of this magnetic field at scales of 10-100 au is maser polarization. We measure the direction of magnetic fields at mas resolution around a sample of massive star-forming regions to determine whether there is a relation between the orientation of the magnetic field and of the outflows. In addition, by estimating the magnetic field strength via the Zeeman splitting measurements, the role of magnetic field in the dynamics of the massive star-forming region is investigated. We selected a flux-limited sample of 31 massive star-forming regions to perform a statistical analysis of the magnetic field properties with respect to the molecular outflows characteristics. We report the linearly and circularly polarized emission of 6.7 GHz CH3OH masers towards seven massive star-forming regions of the total sample with the EVN. The sources are: G23.44-0.18, G25.83-0.18, G25.71-0.04, G28.31-0.39, G28.83-0.25, G29.96-0.02, and G43.80-0.13. We identified a total of 219 CH3OH maser features, 47 and 2 of which showed linearly and circularly polarized emission, respectively. We measured well-ordered linear polarization vectors around all the massive YSOs and Zeeman splitting towards G25.71-0.04 and G28.83-0.25. Thanks to recent theoretical results, we were able to provide lower limits to the magnetic field strength from our Zeeman splitting measurements. We further confirm (based on ~80% of the total flux-limited sample) that the magnetic field on scales of 10-100 au is preferentially oriented along the outflow axes. The estimated magnetic field strength of |B_{||}|>61 mG and >21 mG towards G25.71-0.04 and G28.83-0.2, respectively, indicates that it dominates the dynamics of the gas in both regions.