Gas and star formation in the extreme environments of starburst galaxies

在我们周围的宇宙中，星系是由数十亿颗恒星组成的，其中许多恒星周围都有行星。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。我的研究项目集中在附近的星系，这些星系目前正在经历一场激烈的恒星形成爆发，将气体转变为恒星的速度比我们银河系等星系的速度快10-100倍。具体来说，我研究气体的物理性质，这是恒星形成的燃料，为了理解为什么这些星系中的恒星形成已经进入超速行驶。******虽然这些“星暴星系”现在相对罕见，但这些高恒星形成率在早期宇宙中是正常的，当时富含气体的年轻星系形成了我们今天看到的大多数恒星。然而，由于这些年轻的星系位于非常遥远的地方，即使是最强大的望远镜也很难测量出与恒星和星系形成模拟进行比较所需的详细特性。附近的星暴星系为探测早期宇宙中常见的极端环境（高密度的气体和恒星形成）提供了机会，但现在需要在几百光年的尺度上进行恒星形成模型的有力测试。******我的研究小组将使用强大的射电望远镜——阿塔卡马大型毫米波/亚毫米波阵列（ALMA）的数据，从几个方面来研究极端环境下恒星形成的问题。(1)我们将比较恒星形成的速率和可用气体的数量，以探索支撑经验“恒星形成定律”的物理学的普遍性，这一定律已经在像我们银河系这样的星系中建立起来。(2)我们将首次对星暴星系中单个巨型气体云的数量进行详细测量。云性质的变化也许可以解释强烈的恒星形成：例如，密度越大的云坍塌得更快，这可能会促使气体更快地形成恒星。(3)我们还将利用这些新的云目录来获得关键的校准，这些校准需要将我们的星系射电图像转化为对这些星系中气体质量的精确测量。(4)在局部宇宙中最极端的星暴星系中，由于星系富含气体和尘埃，其中心在可见光下完全看不到，我们将使用更稀有的分子同位素（如12C18O而不是12C16O）来探测星暴持续多久以及它们形成了什么样的恒星。******总的来说，这个研究项目将为我们对今天宇宙中最极端环境下恒星形成的理解提供一个突破，并将对我们对早期宇宙中星系形成的主要时代的理解产生重大影响。

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.