Resolving the Role of Neutral Gas in Galaxy Evolution

加拿大天体物理学未来十年的主要目标之一是了解星系的起源。解开这个谜团是理解我们起源的科学故事的关键一步，它解释了太阳形成的条件，也解释了我们周围的所有恒星。我们广泛地理解恒星是由冷的分子气体云形成的，我们也知道如此形成的短寿命恒星将相对较快地演化和死亡，将它们的物质返回到下一代恒星中。这个重子循环可以解释组成我们星球和我们身体的重元素是如何来自上一代恒星的。然而，驱动重子循环的实际物理机制却鲜为人知。为了理解这一重要的周期，这项研究将使用一套新的望远镜观测来对这些控制星系演化的内部过程进行最有效的普查。具体地说，这项研究将测量恒星形成过程如何随着星系内部局部环境的变化而变化，回答如下问题：恒星在分子气体中形成的速度有多快？是什么物理效应控制了这一速度？什么物理过程会影响其气体转化为恒星的效率？垂死的恒星是如何搅动或破坏其当地环境的？是什么导致气体云冷却并开始形成恒星？我们现在可以通过使用地球和太空中一些最好的望远镜对附近的星系进行高分辨率观测来解决这些问题。我们所有新观测的基本特征是，它们必须能够测量恒星形成的微小细节(高分辨率)。我们使用阿塔卡马大毫米/亚毫米阵列收集了新的数据集，以绘制恒星形成气体云的属性图，并使用哈勃太空望远镜和甚大望远镜来研究最近形成的恒星的属性。我们小组将使用这些数据来测量恒星形成的效率。我们还将使用詹姆斯·韦伯太空望远镜收集新的数据，该望远镜将于2021年底发射，以观察正在形成中的恒星，这将为恒星形成的速度提供新的见解。最后，我们正在使用超大型阵列来研究热气体，它起到了中介的作用：从垂死的恒星接收物质，并冷却形成下一代恒星形成的云。这些观测将测量濒临死亡的恒星如何破坏其局部环境，并为气体云如何开始形成恒星提供新的见解。这些都是理解星系演化的核心问题，但我们的进展有限，因为我们只能对我们银河系的恒星形成进行详细研究。通过观察其他星系，我们最终可以看到恒星的形成是自上而下的，这让我们可以看到恒星的形成是如何连接到更广阔的星系的。

One of the major goals for Canadian astrophysics over the next decade is to understand the origins of galaxies. Unravelling this mystery is a vital step in understanding the scientific story of our origins, explaining the conditions where the Sun formed but also all the stars around us. We understand broadly that stars form out of cold clouds of molecular gas, and we also understand that short-lived stars so formed will evolve and die relatively quickly, returning their material to be incorporated into the next generation of stars. This baryon cycle can explain how the heavy elements that make up our planet and our bodies came from a previous generation of stars. However, the actual physics that drives the baryon cycle is poorly understood. To understand this essential cycle, this research will use a suite of new telescope observations to make the best available census of these internal processes that control galaxy evolution. Specifically, this research will measure how the process of star formation changes in response to the local environments within galaxies, answering questions like: how quickly does star formation take place in molecular gas? What physical effects control that rate? What physical processes affect the efficiency of turning its gas into stars? How do dying stars stir up or destroy their local environments? What causes a cloud of gas to cool and start forming stars? We can now address these questions by making high resolution observations of nearby galaxies using some of the best telescopes on Earth and in space. The essential feature across all our new observations is that they must be able to measure the small details of star formation (high-resolution). We have collected new data sets with the Atacama Large Millimeter/submillimeter array to map out the properties of star forming clouds of gas and the Hubble Space Telescope and the Very Large Telescope to study the properties of the recently formed stars. Our group will use these data to measure the efficiency of star formation. We will also collect new data using the James Webb Space Telescope, which should launch at the end of 2021, to see the stars that are right in the middle of formation, which will provide new insights on how quickly star formation proceeds. Finally, we are using the Very Large Array to study the warm gas, which acts as an intermediary: receiving material from dying stars and cooling down to form the next generation of star-forming clouds. These observations will measure how dying stars disrupt their local environment as well as giving new insights into how gas clouds start forming stars. These are central questions to understanding galaxy evolution, but our progress has been limited because we could only make detailed studies of star formation in our own Milky Way galaxy. By observing other galaxies, we can finally see star formation from the "top down," which allows us to see how star formation connects back to the broader galaxy.