A Holistic View of Gas, Dust, and Metals in Galaxies

恒星之间的气体是星际介质（ISM）的一部分，是理解星系如何演化的基础。然而，这种气体通常只能通过间接的方法来研究，而最广泛使用的示踪剂是一氧化碳（CO）的排放。该项目将利用哈勃太空望远镜、阿塔卡马大型毫米/亚毫米阵列和其他设施对附近星系的新观测，推进对一氧化碳和尘埃作为示踪剂的理解。该团队将研究麦哲伦星云的ISM以及附近星系中心的ISM的CO排放。他们将举办一系列夏季研讨会，旨在帮助从社区学院转到加州大学圣地亚哥分校的学生。转校生是一个多元化的、积极性很高的群体，由于转学后的时间紧迫而处于不利地位，消除这些障碍是扩大代表性不足群体参与的关键一步。间接的方法是必需的，因为大多数氢分子太冷而不能产生发射线。校准作为示踪剂的CO排放量需要了解几个参数：尘气比作为金属丰度的函数，给定温度下粉尘排放量与粉尘质量之间的关系，以及CO与氢气之间的转化，所有这些都随着ISM中的条件而变化。新的观测结果将汇集在一起，以创建一个适用的处方，以确定粉尘发射率、尘气比和转换系数作为环境的函数。这将有助于评估从银河系到遥远的高红移星系的整个范围内的ISM气体含量，并有助于消除当前方法固有的不可避免的系统不确定性。这项工作将对星系中ISM的物理状态产生新的见解，包括分子云的排列及其对星系环境的响应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The gas between stars is part of the interstellar medium (ISM) and is fundamental to understanding how galaxies evolve. However, the gas often can only be studied by indirect methods, and the most widely used tracer is emission from carbon monoxide (CO). This project will advance the understanding of CO and dust as tracers, using new observations of nearby galaxies from the Hubble Space Telescope, the Atacama Large Millimeter/submillimeter Array, and other facilities. The team will study the CO emission from the ISM of the Magellanic Clouds, as well as the ISM in the centers of nearby galaxies. They will conduct a series of summer workshops designed to help transfer students moving from community colleges to UC San Diego. Transfer students are a diverse, highly motivated group, disadvantaged by the compressed timeline after transferring, and removing these barriers is a key step in broadening the participation of under-represented groups. Indirect methods are needed because most of the hydrogen molecules are too cold to produce emission lines. Calibrating CO emission as a tracer requires understanding several parameters: the dust-to-gas ratio as a function of metallicity, the relation between dust emission and dust mass at a given temperature, and the conversion between CO and hydrogen, all of which vary with conditions in the ISM. The new observations will be brought together to create an applicable prescription for dust emissivity, dust-to-gas ratio, and conversion factor, as a function of environment. This will allow assessment of the ISM gas content over the full range from the Milky Way to distant high-redshift galaxies, and help to remove inescapable systematic uncertainties intrinsic to the current approach. The work should yield new insights into the physical state of the ISM in galaxies, including the arrangement of molecular clouds and their response to galactic environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.