Tracing the Cosmic Web in the Far-Infrared Lines as it Builds Massive Galaxies

康奈尔大学的研究小组使用电离碳、氮和氧的远红外光谱线来追踪宇宙时间内星星的形成和星系的聚集，重点是宇宙中星星形成活动高峰期的红移1至4时代，即77亿至120亿年前。这些谱线冷却了气体，并追踪其物理条件，揭示了恒星的表面温度和空间分布。 利用之前的NSF奖项，研究生和本科生设计并建造了用于大型亚毫米望远镜的ZEUS和ZEUS-2光谱仪。 他们发现，在早期，许多最明亮的尘埃星星形成星系形成多达1000恒星每年在扩展，多个千秒差距（kpc）大小的“磁盘”。“他们推测，这些巨大的星星形成盘是由来自宇宙网的气体产生和滋养的，宇宙网包含了宇宙的大部分气体储存库。 他们计划通过ZEUS-2光谱仪在近百万光年尺度上搜索C+和N+线发射中的流入气体来验证这一假设。 发现这种下落气体是为了确认在今天宇宙中大多数恒星形成的时代星系和星星形成的主要模式，并研究今天宇宙中最大星系的形成。 科学将通过教学和推广工作，包括K-12计划，如青少年焦点和GRASSHOPR，进行公开传播。大规模流动的C+和N+线发射的测量将由中央星系的O++观测补充。 这三条线显示了主序星上质量最大的恒星，以及恒星的电离通量和空间范围。 该项目旨在揭示星系如何积累气体成分，这些气体成分转化为恒星，恒星在超新星中演化和死亡，超新星在星系间介质中播种金属。 ZEUS-2/APEX系统是这项工作的最佳选择，因为它的表面亮度灵敏度和大视场。

The Cornell team uses the far-infrared spectral lines of ionized carbon, nitrogen, and oxygen to trace star formation and galaxy assembly over cosmic time with emphasis on the redshift 1 to 4 epoch of peak star formation activity in the Universe, 7.7 to 12 billion years ago. These lines cool the gas and trace its physical conditions and reveal the surface temperatures and spatial distributions of the stars. With previous NSF awards graduate and undergraduate students designed and built the ZEUS and ZEUS-2 spectrometers used on large submillimeter telescopes. They discovered that at early times many of the most luminous dusty star forming galaxies formed up to 1000 stars per year in extended, multiple kiloparsec (kpc) sized "disks." They speculate that these enormous star forming disks are created and nourished by gas that is infalling from the Cosmic Web which contains much of the gas reservoir of the Universe. They plan to test this hypothesis by searching with their ZEUS-2 spectrometer for the inflowing gas in its C+ and N+ line emission at near million light-year scales. To discover this infalling gas is to confirm the major mode of galaxy and star formation during the epoch when most of the stars in today's Universe formed and to investigate the formation of the largest galaxies in today's Universe. Science will be publicly disseminated through teaching and outreach efforts including the K-12 programs like Focus for Teens and GRASSHOPR.Measurement of C+ and N+ line emission from large scale flows will be supplemented by O++ observations of the central galaxy. The three lines reveal the most massive stars on the main sequence and the ionizing flux and spatial extent of the stars. The project aims to reveal how galaxies build up their gas content which is converted into stars that evolve and die in supernovae that seed the intergalactic medium with metals. The ZEUS-2/APEX system is optimal for this work because of its surface brightness sensitivity and large field of view.