The temperature of the circumgalactic and intergalatic medium over cosmic time

在早期宇宙中，星系间介质(IGM)主要充满扩散的氢和氦气体。IGM分布在由薄片和细丝组成的宇宙网络中，由空隙隔开。星系在这些结构的交叉处形成，并由落到星系周围被称为环星系介质(CGM)的区域的IGM气体提供。首席研究员Kim和Wakker将分析档案数据，研究来自IGM的气体吸积和CGM中的星系外流之间的复杂相互作用，CGM控制恒星形成效率并调节星系演化。为了扩大参与，私人投资机构将组织一系列与研究有关的公开讲座，并通过威斯康星大学太空广场开发一个在线展览。PIS还将继续与当地初中和高中合作，增加学生参加一年一度的科学奥林匹克竞赛。PIS将通过基于Voigt轮廓拟合分析来自公开存档的凯克类星体电离吸收观测站数据库(KODIAQ)和紫外线和可见光回声光谱仪(UVES)光谱类星体吸收数据库的~170个类星体光谱，来确定HI、CIV和SiIV离子的吸收线宽度和柱密度，从而估计扩散的CGM/IGM在2z4的温度和湍流。类星体跨越了宇宙恒星形成率在z~4和z~2之间增加三倍的时期，当氦的再电离在z~3显著加热IGM时。PI将利用他们的结果来测试CGM的温度-密度关系以及IGM/CGM在高红移时的气体温度和湍流演变的理论模型。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In the early Universe, the intergalactic medium (IGM) is largely filled with diffuse hydrogen and helium gas. The IGM is distributed in a cosmic web of sheets and filaments, separated by voids. Galaxies form at the intersections of these structures and are fed by IGM gas falling onto regions surrounding galaxies called the circumgalactic medium (CGM). Principal Investigators Kim and Wakker will analyze archival data to study the complex interaction between gas accretion from the IGM and galactic outflows in the CGM, which controls star formation efficiency and mediates galaxy evolution. To broaden participation the PIs will organize a series of research related public talks and develop an online exhibit through the University of Wisconsin Space Place. The PIs will also continue to work with local middle and high schools to increase student participation in the annual Science Olympiad tournament.The PIs will estimate the temperature and turbulence of the diffuse CGM/IGM at 2z4 by determining the absorption line widths and column densities of HI, CIV and SiIV ions based on Voigt profile fitting analysis of ~170 QSO spectra from publicly archived Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) and the Ultraviolet and Visual Echelle Spectrograph (UVES) Spectral Quasar Absorption Database (SQUAD). The quasars span the epoch when the cosmic star formation rate triples between z ~ 4 and z ~ 2, and when helium reionization heats the IGM significantly at z ~ 3. The PIs will use their results to test theoretical models of the temperature-density relation of the CGM and the evolution of gas temperature and turbulence of the IGM/CGM at high redshifts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.