EAPSI: Understanding Cosmic Dust in Lyman-Alpha Emitters

尘埃在宇宙时间上的研究是天文学和天体物理学的一个关键领域，从星系演化和宇宙学到行星形成都具有重要意义。尘埃是恒星死亡时形成的，并扩散到星际介质中；其中一些会形成下一代的恒星和行星，而大部分会留在星际介质中。这种尘埃对紫外线和光学光进行再处理，吸收它并将能量重新发射到中远红外线中。即使是少量或中等数量的尘埃也会极大地影响观测到的星系特性。该奖项支持研究早期宇宙中星系的尘埃特性，这些星系被认为是银河系型星系的祖先。这项研究直到最近才成为可能，因为阿塔卡马大型毫米波阵列（ALMA）的投入使用，它可以直接探测到这些微小星系中尘埃的热发射。这项研究将与东京大学的Masami Ouchi教授合作进行，对这些星系进行首次同类研究，开始了一项具有多年成果潜力的合作。具体来说，这项工作将使用Conroy等人开发的柔性恒星群合成（FSPS）软件进行光谱能量分布（SED）拟合。FSPS使用Draine和Lee（2007）的尘埃模型，使用尘埃质量、多环芳烃分数和尘埃粒度分布这三个参数来参数化宇宙尘埃。由于宇宙中的大部分光来自尘埃发射，因此了解这些特性以及它们在宇宙生命周期中的变化是至关重要的。利用深ALMA数据，我们可以探测Lyman-alpha巡天在这些领域发现的众多恒星形成星系的尘埃发射。这些莱曼α发射体通常是小的、低质量的星系，它们将形成银河系大小的星系。明亮的莱曼- α线提供了一个很好的方法来寻找研究小星系，否则很难找到。了解它们的尘埃特性对我们进一步了解这些星系和研究银河系可能的历史至关重要。NSF EAPSI奖是与日本科学促进会合作资助的。

The study of dust over cosmic time is a key field of astronomy and astrophysics that has implications from galaxy evolution and cosmology to planet formation. Dust forms as stars die and is spread into the interstellar medium; some is then formed into the next generation of stars and planets, while a large fraction stays in the interstellar medium. This dust reprocesses ultraviolet and optical light, absorbing it and re-emitting the energy into the mid- and far-infrared. Even a small or moderate amount of dust can greatly affect the observed properties of galaxies. This award supports research to study the dust properties of galaxies in the early universe, which are thought to be progenitors to Milky Way type galaxies. This study has only become possible very recently with the commissioning of the Atacama Large Millimeter Array (ALMA), which can directly detect the thermal emission from dust in these tiny galaxies. The research will be conducted in partnership with Prof. Masami Ouchi of the University of Tokyo to do a first-of-a-kind study of these galaxies, initiating a collaboration with the potential to be fruitful for many years.Specifically, this work will use spectral energy distribution (SED) fitting using the Flexible Stellar Population Synthesis (FSPS) software developed by Conroy et al. FSPS uses the dust models of Draine and Lee (2007) to parametrize cosmic dust using three parameters, dust mass, PAH fraction, and dust grain size distribution. As most of the light in the universe is from dust emission, understanding these properties, and how they change over the lifetime of the universe, is of critical concern. Using deep ALMA data, we can probe for dust emission from the numerous star forming galaxies discovered in Lyman-alpha surveys in these fields. These Lyman-alpha emitters are generally small, low mass galaxies that will form into Milky Way sized galaxies. The bright Lyman-alpha line provides an excellent way to find a study small galaxies otherwise very difficult to find. Understanding their dust properties is crucial to further our understanding of these galaxies and investigate possible histories of the Milky Way. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.