How Do Galaxies End Their Star-Formation?

这个项目将研究从恒星形成向非恒星形成过渡的星系的数量，比以前可能的精度更高。该奖项支持的首席研究人员和研究生将结合斯隆数字天空调查的光学波长数据、星系演化探测器(GALEX)航天器的紫外线数据和广域红外调查探测器(WISE)航天器的中红外数据，来识别过渡星系，并限制它们的金属丰度、恒星形成率、尘埃消光、恒星质量和低红移时的活动核含量。然后，他们将使用Primus，这是一项12万星系调查，对红移范围在0.2到1.0之间进行采样，结合GALEX和斯皮策太空望远镜的数据，在红移更高的情况下进行类似的分析。目标是(1)获得一次准确和有代表性的过渡期人口普查；(2)确定孤立星系中的恒星形成是否与星系团人口中的恒星形成以同样的方式关闭；以及(3)确定活动星系核是否与过渡期现象有关。除了支持研究生培训外，该项目还将能够扩展美国航天局-斯隆星系地图集，将新发布的WISE数据纳入其中，并在现有的网络界面内开发教育和外联工具。

This project will investigate the population of galaxies that are in transition from star-forming to non-star-forming, with greater accuracy than was previously possible. The Principal Investigator and graduate students supported by the award will combine optical-wavelength data from the Sloan Digital Sky Survey, ultraviolet data from the Galaxy Evolution Explorer (GALEX) spacecraft, and mid-infrared data from the Wide-Field Infrared Survey Explorer (WISE) spacecraft, to identify transition galaxies and to constrain their metallicities, star-formation rates, dust extinctions, stellar masses, and active nucleus content at low redshift. They will then use PRIMUS, a 120,000 galaxy survey sampling the redshift range between 0.2 and 1.0, combined with GALEX and Spitzer Space Telescope data, to perform a similar analysis at higher redshift. The objectives are (1) to obtain an accurate and representative census of the transition population; (2) to determine whether star-formation is turning off the same way in isolated galaxies as in cluster populations; and (3) to determine whether active galactic nuclei are related to the transition phenomenon. In addition to supporting graduate student training, the project will enable expansion of the NASA-Sloan Atlas of galaxies to include newly released WISE data and development of educational and outreach tools within the existing web interface.