Density distributions, magnetic field structures, and fragmentation in high-mass star formation
Density distributions, magnetic field structures, and fragmentation in high-mass star formation
复制标题
高质量恒星形成过程中的密度分布、磁场结构和碎裂
DOI：
10.1051/0004-6361/202348117
复制
发表时间：
2024
影响因子：
6.5
通讯作者：
Beuther H
中科院分区：
文献类型：
--
作者：
Beuther H
上下文高质量恒星形成区的碎裂取决于各种物理参数，包括密度、磁场和湍流气体性质。我们评估的重要性的密度和磁场结构的关系，在高质量星星形成的碎裂性能。利用IRAM 30 m望远镜观测了大秒差距尺度的Stokes-1毫米尘埃连续辐射，利用亚毫米阵列观测了中等尺度（<0. 1 pc）的偏振亚毫米尘埃辐射，观测了20个大质量恒星形成区的样本，定量分析了这些区域的碎裂行为对密度和磁场结构的依赖性。基于IRAM 30 m数据，我们推断出具有典型幂律斜率约为1.5的区域的密度分布。在较大的团块尺度（~1 pc）上的密度结构的幂律斜率与较小的核心尺度（<0.1pc）上的碎片数之间没有明显的相关性。将大尺度单碟密度剖面与早期在较小空间尺度上从干涉观测中获得的密度剖面进行比较，我们发现较小尺度的幂律斜率更陡，通常约为2.0。向更大尺度的扁平化与恒星形成区域嵌入在更大的云结构中是一致的，这些云结构在远离特定核心的地方密度不会降低。几个区域的磁场似乎与指向致密中心核的沉积结构一致。此外，我们发现不同的偏振结构，一些区域表现出中心偏振孔，而其他区域显示偏振发射也朝向中心峰值位置。尽管如此，偏振强度与斯托克斯强度成反比，近似遵循幂律斜率，即Δ SI-0.62。我们估计磁场强度在~0.2和~4.5 mG之间，我们发现磁场强度和该地区的碎片化水平之间没有明显的相关性。湍流能量与磁场能量的比较表明，它们在这个样本中的重要性大致相同。质量流量比在~2和~7之间，与坍缩的恒星形成区一致。在现今的大尺度密度结构、磁场强度和区域的小尺度碎裂特性之间没有发现明显的相关性，这表明高质量恒星形成区域的碎裂可能不会受到初始密度分布和磁场特性的强烈影响。然而，考虑到有限的演变范围和空间尺度的CORE分析，未来的研究方向应该包括更好地类似于初始条件的年轻地区的密度结构分析，以及连接所观察到的中尺度磁场结构与更大尺度的磁场的母体分子云。
Context. The fragmentation of high-mass star-forming regions depends on a variety of physical parameters, including density, the magnetic field, and turbulent gas properties.Aims. We evaluate the importance of the density and magnetic field structures in relation to the fragmentation properties during high-mass star formation.Methods. Observing the large parsec-scale StokesImillimeter dust continuum emission with the IRAM 30 m telescope and the intermediate-scale (<0.1 pc) polarized submillimeter dust emission with the Submillimeter Array toward a sample of 20 high-mass star-forming regions allows us to quantify the dependence of the fragmentation behavior of these regions on the density and magnetic field structures.Results. Based on the IRAM 30 m data, we infer density distributionsn∝r−pof the regions with typical power-law slopesparound ~1.5. There is no obvious correlation between the power-law slopes of the density structures on larger clump scales (~1 pc) and the number of fragments on smaller core scales (<0.1 pc). Comparing the large-scale single-dish density profiles to those derived earlier from interferometric observations at smaller spatial scales, we find that the smaller-scale power-law slopes are steeper, typically around ~2.0. The flattening toward larger scales is consistent with the star-forming regions being embedded in larger cloud structures that do not decrease in density away from a particular core. The magnetic fields of several regions appear to be aligned with filamentary structures that lead toward the densest central cores. Furthermore, we find different polarization structures; some regions exhibit central polarization holes, whereas other regions show polarized emission also toward the central peak positions. Nevertheless, the polarized intensities are inversely related to the StokesIintensities, following roughly a power-law slope of ∝SI−0.62. We estimate magnetic field strengths between ~0.2 and ~4.5 mG, and we find no clear correlation between magnetic field strength and the fragmentation level of the regions. A comparison of the turbulent to magnetic energies shows that they are of roughly equal importance in this sample. The mass-to-flux ratios range between ~2 and ~7, consistent with collapsing star-forming regions.Conclusions. Finding no clear correlations between the present-day large-scale density structure, the magnetic field strength, and the smaller-scale fragmentation properties of the regions, indicates that the fragmentation of high-mass star-forming regions may not be affected strongly by the initial density profiles and magnetic field properties. However, considering the limited evolutionary range and spatial scales of the presented CORE analysis, future research directions should include density structure analysis of younger regions that better resemble the initial conditions, as well as connecting the observed intermediate-scale magnetic field structure with the larger-scale magnetic fields of the parental molecular clouds.