Gas and star formation in the extreme environments of starburst galaxies

在我们周围的宇宙中，星系由数十亿颗恒星组成，其中许多恒星都有行星围绕着它们旋转。这意味着我们必须首先了解恒星是如何形成的，然后才能了解星系或行星的形成。我的研究项目专注于附近的星系，这些星系目前正在经历恒星形成的强烈爆发，将气体转化为恒星的速度比我们银河系等星系的速度快10-100倍。具体地说，我研究了作为恒星形成燃料的气体的物理性质，以了解为什么这些星系中的恒星形成已经进入超速状态。 虽然这些“恒星爆发星系”现在相对罕见，但在早期宇宙中，这些高速率的恒星形成是正常的，当时我们看到的大多数恒星都是由富含气体的年轻星系形成的。然而，由于这些年轻的星系位于令人难以置信的很远的距离，即使是最强大的望远镜也发现很难测量与恒星和星系形成的模拟相比较所需的详细性质。附近的星爆星系提供了探索极端环境(高密度气体和恒星形成)的机会，这种极端环境在早期宇宙中很常见，但现在已经达到几百光年的规模，需要对恒星形成模型进行强有力的测试。 我的研究团队将使用来自阿塔卡马大毫米/亚毫米阵列(ALMA)的强大射电望远镜的数据，从几个方面解决极端环境中恒星形成的问题。(1)我们将比较恒星形成的速率和可用气体的数量，以探索建立在像我们银河系这样的星系中的经验“恒星形成定律”所依据的物理学的普遍性。(2)我们将首次对恒星爆发星系中单个巨型气体云的数量进行详细测量。云层性质的变化可能解释了恒星形成的强度：例如，密度较高的云团崩塌的速度会更快，这可能会驱动气体更快地形成恒星。(3)我们还将使用这些新的云表来获得关键的校准，这些校准是将我们的星系射电图像转换为对这些星系中气体质量的准确测量所必需的。(4)在局部宇宙中最极端的星暴星系中，我们将使用更稀有的分子同位素(如12C18O而不是12C16O)来探测星暴持续多长时间以及它们形成了什么类型的恒星。 总体而言，这一研究计划将为我们理解当今宇宙中最极端环境下的恒星形成提供突破，并将对我们理解早期宇宙中星系形成的主要时期产生强烈影响。

In the universe around us, galaxies are made up of billions of stars, many with planets circling around them. This means that we must first understand how stars form before we can understand the formation of either galaxies or planets. My research program focuses on nearby galaxies that are currently experiencing an intense burst of star formation, turning gas into stars at rates that are 10-100 times faster than the rate in galaxies like our own Milky Way. Specifically, I study the physical properties of the gas that is the fuel for star formation, in order to understand why the star formation in these galaxies has kicked into overdrive. Although these “starburst galaxies” are now relatively rare, these high rates of star formation were normal in the early universe, when young galaxies rich in gas were forming most of the stars we see today. However, because these young galaxies lie at incredibly large distances, even the most powerful telescopes find it extremely difficult to measure the detailed properties that are needed for comparison with simulations of star and galaxy formation. Nearby starburst galaxies provide the opportunity to probe the extreme environments (high densities of gas and star formation) that were common in the early universe, but now on the scales of a few hundred light years that are required to provide strong tests of star formation models. My research team will use data from a powerful radio telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), to attack the problem of star formation in extreme environments along several fronts. (1) We will compare rates of star formation with the amount of available gas to probe the universality of the physics that underpins the empirical “star formation law” that has been established for galaxies like our own Milky Way. (2) We will make the first detailed measurements of the populations of individual giant gas clouds in starburst galaxies. Changes in cloud properties may explain the intense star formation: for example, higher density clouds will collapse faster, which could drive the gas to form stars more rapidly. (3) We will also use these new cloud catalogs to obtain critical calibrations that are needed to turn our radio images of galaxies into accurate measurements of the mass of gas in those galaxies. (4) In the most extreme starburst galaxies in the local universe, galaxies so rich in gas and dust that their centres are completely hidden from view in visible light, we will use rarer molecular isotopes (such as 12C18O instead of 12C16O) to probe how long the starbursts last and what kinds of stars they form. Overall, this program of research will provide a breakthrough in our understanding of star formation in the most extreme environments in the universe today and will have strong impact on our understanding of the main epoch of galaxy formation in early universe.