Stellar Populations in Star-forming Galaxies

星系的形态和化学演化是一个引人入胜的课题：宇宙是如何从混沌的、化学物质贫乏的物质转变成各种各样的、化学元素丰富的星系的？在过去的十年里，随着成像光谱仪的发展，这个话题获得了更多的兴趣，可以更好地掌握附近星系中恒星形成的小规模物理。恒星群的研究是回答星系演化领域问题的重要途径：恒星群，因为它们塑造了星系的外观，保留了负责它们形成的事件的特征，因此，星系演化。在过去的几年里，我的研究主要集中在恒星形成星系中年轻恒星群的描述上。努力致力于发展SITELLE，这是一种建立在qubec的可见光成像傅立叶变换光谱仪，并领导了SIGNALS，这是一项在加拿大-法国-夏威夷望远镜上使用SITELLE进行的国际遗产调查。已经在进行中的信号（2018-2022）将以平均20pc的空间分辨率揭示约40个附近星系中超过50,000个HII区域的3D特性，即围绕年轻恒星形成群体的电离气体区域。在开发识别HII区域和系统测量其性质的工具的同时，这里提出的研究将集中在信号不规则星系子样本中的低金属丰度区域，以及在各种环境下HII区域性质的比较。其中，要绘制详细的亮度函数。为了获得年轻群体的最佳参数，来自YPULS（信号星系的一项UVIT调查，我是该项调查的共同负责人）的远紫外线数据将成为分析的一部分。该信息是用于描述HII区域和估计返回到星际介质的能量的光电离代码的重要输入。为了重建星系完整的恒星形成历史，将使用各种合成代码来研究较老的恒星群，例如基于SITELLE的吸收谱线光谱。需要解决的更具体的问题与星系中的化学丰度变化、星际介质中的小型和大型混合过程、恒星种群初始质量函数以及漫射电离气体的起源和对恒星形成速率的影响有关。信号的同质性和统计意义的数据库将导致原创和重要的出版物。七名学生将参与这项研究计划。他们将与SITELLE数据和60多名SIGNALS专家（42%为女性，具有巨大的文化多样性）合作，为学生的形成和职业生涯提供独特的机会。

STELLAR POPULATIONS IN STAR-FORMING GALAXIES The morphological and chemical evolution of galaxies is a fascinating subject: how did the Universe transform itself from chaotic and chemically poor material into a wide variety of galaxies with rich chemical elements? During the last decade, this topic has gained even more interests with the development of imaging spectrographs, allowing a better grip on the small-scale physics of star formation in nearby galaxies. The study of stellar populations is an important avenue to answer questions in the field of galaxy evolution: stellar populations, as they sculpt the galaxy appearances, retain the signature of events that have been responsible for their formation and therefore, galaxy evolution. In the past years, my research has mainly focused on the description of young stellar populations in star-forming galaxies. Efforts have been dedicated to the development of SITELLE, an imaging Fourier transform spectrograph in the visible built in Québec, and to the leadership of SIGNALS, an international legacy survey with SITELLE at the Canada-France-Hawaii Telescope. SIGNALS, already underway (2018-2022), will reveal the 3D properties of more than 50 000 HII regions, i.e. ionized gas regions surrounding young star-forming populations, in ~40 nearby galaxies at an average spatial resolution of 20 pc. The proposed research here, while developing tools to identify the HII regions and measure their properties in a systematic way, will be concentrated on the low-metallicity regions in a subsample of SIGNALS irregular galaxies, and on the comparison of the HII region properties in various environments. Among others, detailed luminosity functions are to be drawn. Far-ultraviolet data from YPULS (a UVIT survey of the SIGNALS galaxies, for which I am co-PI) will be part of the analysis in order to get the best parameters for the young populations. This information is an important input for the photoionization codes used to describe the HII regions and to estimate the energy returned into the interstellar medium. In order to rebuild the complete star-formation history of the galaxies, older stellar populations will be studied using various synthesis codes based, for example, on absorption lines spectra with SITELLE. More specific questions to be addressed are related to chemical abundance variations in galaxies, small- and large-scale mixing processes in the interstellar medium, the stellar population initial mass function, and the origin and effect of the diffuse ionized gas on the star-formation rate. The homogeneous and statistically significant database of SIGNALS will lead to original and important publications. Seven students will be involved in this research program. They will work with SITELLE data and more than 60 SIGNALS experts (42% women, with great cultural diversity), a unique opportunity for the students formation and career.