High Spectral Resolution Observations of the Interstellar Medium in the Nuclei of Nearby Galaxies using Herschel and SOFIA

Herschel和SOFIA上的外差仪器将首次提供星系核中ISM主要冷却线的广泛清单，采样银河系中几乎找不到的各种物理条件。以前与KAO和ISO的观测留下了许多悬而未决的问题，FIR观测站具有高角度和高光谱分辨率，现在可以解决这些问题。我们计划关注以下三个关键问题：1)星系核中发射恒星形成气体的物理条件是什么，以及冷却发射告诉我们加热气体的主要途径是什么？这也将告诉我们恒星形成在agn上的重要性，在激波上的FUV光子，或者在x射线上的FUV光子。2)第二个关键问题是[CII]排放的来源，这是ISM最重要的冷却线。ISM不同阶段的相对重要性还不清楚，将随着物理环境的变化而变化。3)将麦哲伦云纳入样本将允许在小空间尺度上研究金属丰度的变化如何影响ISM的其他物理和化学性质。

The heterodyne instruments on Herschel and SOFIA will provide for the first time an extensive inventory of the major cooling lines of the ISM in galactic nuclei sampling a wide range of physical conditions hardly found in the Milky Way. Previous observations with the KAO and ISO have left many questions unanswered which the FIR observatories with their high angular and high spectral resolutions can now address. We plan to focus on the following three key questions: 1) What are the physical conditions of the emitting star-forming gas in galactic nuclei, and what does the cooling emission tell us about the major pathways heating the gas? This will also tell us the importance of star formation over AGNs, of FUV photons over shocks, or of FUV photons over X-rays. 2) A second key questions is the origin of [CII] emission, the most important cooling line of the ISM. The relative importance of the different phases of the ISM is yet unclear will vary with physical environment. 3) Including the Magellanic Clouds in the sample will allow to study at small spatial scales how variations in the metallicity influence the other physical and chemical properties of the ISM.