Exploring the Star Formation History of the Universe Using ZEUS-2

宇宙中的星星形成活动在大爆炸后20亿到60亿年达到顶峰，对应的红移在1到3之间。这些恒星的大部分辐射能量被新生分子云中的尘埃吸收，在光谱的远红外部分重新辐射，并且今天可以观察到红移到亚毫米。为了测量这些星系的内禀光度和星星形成率，必须在亚毫米波段进行观测。此外，形成星星的星际介质（ISM）被这些波长下可观察到的原子谱线辐射冷却，因此亚毫米光谱学对于理解星星形成过程至关重要。该项目利用ZEUS和ZEUS-2摄谱仪的科学能力，由先进技术仪器（ATI）和主要研究仪器（MRI）计划提供资金开发，以观察高红移星系中碳，氮和氧的特定原子精细结构线。ZEUS-2将用于加州理工学院亚毫米波天文台（CSO）和阿塔卡马探路者实验（APEX），以及其他空间和地面的毫米波、亚毫米波和远红外跟踪观测，以便：（1）将正在进行的[CII]发射线调查扩展到更深的红移和更低的光度，跟踪星星形成模式随时间的变化;（2）在相同的红移范围内观测[OI]和[NII]线，以追踪恒星种群的变化;（3）在红移约为2时观测亮度与银河系相当的引力透镜星系;（4）研究星暴与活动星系核之间的联系。这些观测结果将是一个关键的垫脚石，将赫歇尔太空望远镜的发现与未来阿塔卡马大型毫米/亚毫米阵列（阿尔马）的空间分辨调查联系起来。ZEUS-2还为仪器开发和科学机会奠定了基础，这些机会将由拟议的25米Cerro Chajnantor Atacama望远镜（CCAT）上的未来光谱仪实现。该项目将支持多个研究生和本科生的积极参与，许多来自代表性不足的群体，在仪器开发和研究。

Star formation activity in the universe peaked 2 to 6 billion years after the Big Bang, corresponding to redshifts between 1 and 3. Most of the radiant energy from these stars was absorbed by dust in their nascent molecular clouds, re-radiated in the far infrared part of the spectrum, and can be observed today redshifted to the submillimeter. To measure the intrinsic luminosities and star formation rates of these galaxies, one must therefore observe in the submillimeter bands. Moreover, the star forming interstellar medium (ISM) is cooled by atomic spectral line radiation observable at these wavelengths; hence submillimeter spectroscopy is critical for understanding the star formation process. This project makes use of the scientific capabilities of the ZEUS and ZEUS-2 spectrographs, developed with prior funding from the Advanced Technologies & Instrumentation (ATI) and Major Research Instrumentation (MRI) programs, to observe specific atomic fine-structure lines of carbon, nitrogen, and oxygen in high-redshift galaxies. ZEUS-2 will be used on the Caltech Submillimeter Observatory (CSO) and the Atacama Pathfinder Experiment (APEX), together with other space- and ground-based follow-up observations in the millimeter, submillimeter, and far infrared in order to: (1) extend an ongoing survey of [CII] emission lines to deeper redshift and lower luminosity, tracing the change is star formation mode over time; (2) observe [OI] and [NII] lines in the same redshift range, to trace the changes in stellar populations; (3) observe gravitationally lensed galaxies comparable to the Milky Way in luminosity at redshifts around 2; and (4) study the connection between starbursts and active galactic nuclei. These observations will represent a key stepping stone linking discovery with the Herschel Space Telescope to future spatially resolved investigations with the Atacama Large Millimeter/Submillimeter Array (ALMA). ZEUS-2 also lays the ground-work for instrument development and science opportunities that will be enabled by a future spectrometer on the proposed 25-meter Cerro Chajnantor Atacama Telescope (CCAT). The project will support the active involvement of multiple graduate and undergraduate students, many from under-represented groups, in instrument development and research.