High Frequency Channel for CHAI

基于我们为科隆大学的赫歇尔和索菲亚等主要观测设施开发传统仪器的经验，我们目前正在建造Chajnantor外差阵列仪器（CHAI），将部署在智利北部海拔5600米的Cerro Chajnantor上的CCAT天文台的Fred Young亚毫米望远镜（FYST）上。FYST是一种新型的6米口径望远镜，计划于2024年首次亮相。它将使亚毫米波长的高灵敏度广域观测成为可能。它的仪器将处理科学主题，从恒星的形成和银河系和附近星系的星际介质的演变，到早期宇宙和宇宙学中的星系。CHAI是特别重要的，因为它将是唯一一个通过其多像素外差光谱仪提供高分辨率光谱的仪器，其低频通道（LFA）的观测频率从400到490 GHz。因此，根据CCAT联盟合作伙伴协议的保证，可用观测时间的25%将分配给CHAI及其科学案例。我们的目标是更好地利用CCAT观测站良好的大气条件，在CHAI上增加一个高频率频道（HFA），工作在800 GHz大气窗口。通过同时观测LFA和HFA，仪器的性能将加倍，在这些频率上，它已经具有前所未有的制图速度和光谱灵敏度。更重要的是，第二个频率窗口提供了独特的新科学，这对于充分解决CCAT天文台关键计划GEco（银河生态项目）中定义的研究课题是必要的。这项调查的目的是研究银河系和附近星系的星际介质中的物质循环，从云层的聚集到细丝、中心和核心的形成，最终形成恒星，这些恒星反过来提供恒星反馈。完整的科学案例需要高频观测，因为它们提供了宝贵的信息，不仅可以解释我们的低频观测，还可以解释其他大规模的调查，以及我们对星际介质中结构的形成及其演化的理解。该提案的关键目标是确保为建造CHAI HFA提供资金，从而实现和收获从DFG和合作伙伴资源获得FYST望远镜资金时所设想的科学。

Building on our experience with developing legacy instruments for major observing facilities like Herschel and SOFIA at University of Cologne, we are currently building the Chajnantor Heterodyne Array Instrument (CHAI), to be deployed on the Fred Young Submillimeter Telescope (FYST) of the CCAT observatory on top of Cerro Chajnantor in northern Chile at 5600 m altitude. FYST is a novel 6 m aperture telescope scheduled to see first light in 2024. It will enable highly sensitive wide field observations at submillimeter wavelengths. Its instruments will address science topics ranging from the formation of stars and the evolution of the interstellar medium in the Milky Way and nearby galaxies to galaxies in the early universe and cosmology. CHAI is of particular importance, since it will be the only instrument providing high resolution spectroscopy through its multi-pixel heterodyne spectrometer covering observing frequencies from 400 to 490 GHz in its low frequency channel (LFA) at first light. Accordingly, 25% of the available observing time will be allocated to CHAI and its science cases, as guaranteed in the CCAT consortium partner agreement. We here aim to even better exploit the excellent atmospheric conditions at the CCAT observatory site by adding a high frequency channel (HFA) to CHAI, operating in the 800 GHz atmospheric window. Through simultaneous observation of the LFA and HFA, the performance of the instrument will be doubled, on top of its already unprecedented mapping speed and sensitivity for spectroscopy at these frequencies. More importantly, the second frequency window gives access to unique new science, which is necessary to fully address the research topics defined in the CCAT observatory key program GEco, the Galactic Ecology project. This survey is designed to study the matter cycle in the interstellar medium of the Milky Way and nearby galaxies from the assembly of clouds to the formation of filaments, hubs and cores within them, and eventually stars, which in turn provide stellar feedback. The full science case requires the high frequency observations as they give invaluable information for the interpretation not only of our low frequency observations, but also other large scale surveys and our understanding of the formation of structures in the interstellar medium and their evolution. The key objectives of this proposal are to secure funding to build the CHAI HFA, and thus, to enable and harvest the science that has been envisioned when securing the funding for thr FYST telescope from the DFG and partner resources.