Collaborative Research: Carriers, Charge State and Diagnostic Use of the Long-Mysterious Diffuse Interstellar Bands

这项工作调查了哪些原子、离子、小分子和大分子会导致某些星际吸收特征，即“星际扩散带”(DIBS)。自20世纪20年代以来，与这些星际带家族相关的大约600条吸收线已为人所知，但它们与哪些特定分子的联系仍然未知。在这里，在原子和分子光谱学、星际气体和尘埃以及实验室化学方面拥有不同专业知识的研究人员聚集在一起，解决这个长期悬而未决的问题。其方法是汇编和组织数据库中现有的观测数据，并增加对大约220颗恒星的DIB的新测量，以评估和寻找不同的DIB吸收特征以及其他星际参数(如密度和电离态)之间的经验关系。现有的所有光谱宽度到统一极限的DIBS列表通过新的观测得到扩展，包括仅在某些物理条件下出现的宽线和窄线。为此，将汇编一份照亮这些星际区域的新的恒星地图集。另一个目标是观测某些星际扩散云，以获得DIBS的类型和吸收强度随密度和电离态的增加而变化，这与特定化合物的空间分布和云中正在进行的反应有关。团队成员已经保证可以进入观测设施(例如阿帕奇点天文台)来完成这部分工作。只要导致DIB吸收的化合物类型(怀疑分子的原子超过15个)仍然难以捉摸，就不可能完全解释星际介质的化学清单和过程。DIB载体的识别将是理解恒星和行星形成的分子云中化学物质清单的重要一步。这一合作项目的跨学科性质非常强。它为本科生和研究生提供了解决与多个学科相关的问题的机会。

This work investigates which atoms, ions, small and large molecules cause certain interstellar absorption features known as "Diffuse Interstellar Bands" (DIBs). About 600 absorption lines associated with these families of interstellar bands are known since the 1920s but their association which specific molecules is still unknown. Here researchers with different expertise in atomic and molecular spectroscopy, interstellar gas and dust, and laboratory chemistry, come together to tackle this long-standing open question. The approach is to compile and organize existing observations in databases and to add new measurements of DIBs seen toward about 220 stars to assess and to search for empirical relations between the different DIB absorption features as well as other interstellar parameters such as density and ionization state. The existing list of DIBs of all spectral widths to uniform limit is expanded with new observations to include broad and narrow lines that only appear under certain physical conditions. For this purpose, a new atlas of stars illuminating such interstellar regions will be assembled. Another goal is to observe certain diffuse interstellar clouds to obtain the types and absorption strengths of DIBs as a function of increasing density and ionization state, which relates to the spatial distribution of particular compounds and on-going reactions within the cloud. The team members have guaranteed access to observing facilities (e.g., Apache Point Observatory) to do this part of work.As long as the types of compounds (molecules with more than 15 atoms are suspected) responsible for the DIB absorptions remain elusive, it is not possible to fully account for the chemical inventory and processes of the interstellar medium. The identification of the carriers of the DIBs will be a major step forward in understanding the chemical inventory in molecular clouds from which stars and planets form.The interdisciplinary nature of this collaborative project is very strong. It provides undergraduate- and graduate students with opportunities to work on problems related to more than one discipline.