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3种算法检测银河画卷13CO云团形态的对比分析

Morphological Comparison of Three Algorithms for 13CO Clump Detection in the Milky Way Imaging Scroll Painting

  • 摘要: 分子云团检测算法的客观评价是解析星际介质层次化结构、揭示恒星形成物理过程的关键环节, 然而现有研究缺乏对真实观测数据中不同算法所检测的云团形态轮廓差异及其结构表征能力的系统对比.该研究以银河画卷3个典型区域银经(galactic longitude, l) 15.25^\circ\leq l \leq 18.25^\circ、银纬(galactic latitude, b) 0^\circ\leq b\leq 1.5^\circ, 100^\circ \leq l \leq 110^\circ、|b|\leq 5.25^\circ, 180^\circ \leq l \leq190^\circ、|b|\leq 5.25^\circ中13CO (J=1-0)谱线数据为样本, 用FellWalker、FacetClumps、Dendrograms算法对分子云团进行检测和参数分析. 利用RJ (Rotated J-values)-plots方法对13CO云团形态分类, 结果表明FacetClumps算法在3个区域中检测的致密准圆形云团所占比例更高, 均在85%以上, 而FellWalker和Dendrograms算法检测的云团中伸长形结构多于FacetClumps算法, 比例为20%\sim40%. 根据M16区数据和C18O对应体数量比较分析, FellWalker和FacetClumps这两种算法检测的中心致密准圆形类的13CO云团中包含更多的C18O对应体, 比例分别达到77%、91%. 经计算13CO云团的\rm H_2柱密度并分析其与致密程度的相关性发现, 云团的致密程度随柱密度的提高而增大, 且较高柱密度的13CO云团更易包含C18O对应体.

     

    Abstract: The objective evaluation of molecular clump detection algorithms is pivotal for unraveling the hierarchical structure of the interstellar medium and for revealing the physical processes that drive star formation. However, systematic comparisons of morphological differences and structural characterization capabilities among algorithms applied to real observational data are still lacking. We apply FellWalker, FacetClumps, and Dendrograms to 13CO (J=1-0) spectral data from three representative regions of the Milky Way Imaging Scroll Painting (MWISP): 15.25^\circ\leq l\leq18.25^\circ,\; 0^\circ\leq b\leq 1.5^\circ; 100^\circ\leq l\leq110^\circ;\;|b|\leq5.25^\circ; and 180^\circ\leq l\leq190^\circ,\;|b|\leq5.25^\circ. Using RJ-plots to classify the morphologies of 13CO clumps, we find that FacetClumps identifies a substantially higher fraction of centrally overdense, quasi-circular clumps in all three regions (all exceeding 85%), whereas FellWalker and Dendrograms detect a larger share of elongated structures, ranging from 20% to 40% of the detected clumps. A comparison based on C18O counterpart statistics in the M16 field shows that the centrally overdense, quasi-circular 13CO clumps found by FellWalker and FacetClumps contain C18O counterparts at rates of 77% and 91%, respectively. We further compute H_2 column densities for the 13CO clumps and examine their relation to compactness. We find that clumps with higher column densities tend to be more compact, and high-column-density 13CO clumps are more likely to have associated C18O counterparts.

     

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