RII Track-4:@NASA: Bluer and Hotter: From Ultraviolet to X-ray Diagnostics of the Circumgalactic Medium

自从第一批望远镜发现星系以来，它们明亮的螺旋形外观就使人类眼花缭乱。然而，这张星系的图片非常不完整，只包含了它们的星光。这些恒星，就像我们的太阳一样，必须从银河系内外的巨大气体供应中形成，而这些气体是人类肉眼无法看到的。因此，了解新一代恒星如何以及为什么可能会或可能不会形成（即，星系是“活的”还是“死的”）需要在巨大的波长范围内进行观测，因为星系内部和周围的气藏的温度可能跨越10万倍。我们现在知道，气体流入和流出星系是一种复杂的相互作用，就像自然界中经常遇到的生态系统一样。这些生态系统的机制是我们宇宙起源的核心。美国国家科学院（National Academy of Sciences）已经将这些“宇宙生态系统”作为未来十年乃至更长时间内天体物理学研究的国家重点。首席研究员（PI）的研究小组一直专注于宇宙生态系统中较冷的气体，那些在紫外线和可见光波段可探测到的气体，但需要x射线观察的较热的阶段起着关键作用。该奖学金将装备PI在新墨西哥州立大学的研究小组，从全面的多波长角度解决这一国家优先事项。该项目将利用美国宇航局戈达德太空飞行中心的x射线专业知识来培训PI和一名x射线天文观测研究生。研究团队将进行三项关键调查，将我们目前的专业知识与新获得的x射线技术结合起来，同时使用获得大量美国投资的x射线设备。气体渗透宇宙生态系统的观测特征主要是在紫外线（UV）和光学波长，它们对低温（10^4 K）和温热（10^5−10^6 K）气体敏感。然而，星系形成理论越来越指向在x射线中观察到的更热的阶段（10^6 K），因为它掌握着宇宙生态系统中关键过程的答案。我们正站在一个激动人心的时刻，即将发布eROSITA All Sky Survey （eRASS）的数据，美国和日本领导的高光谱分辨率XRISM x射线望远镜将于2023年发射，x射线社区不知疲倦地为美国在未来十年内发射的下一个x射线太空望远镜开发任务概念（另一个国家科学院的建议）。研究小组将与美国宇航局戈达德太空飞行中心的天体物理学家合作，在新墨西哥州立大学（NMSU）建立必要的研究基础设施，以抓住这些新兴的机会。为此，我们将开展涉及x射线分析关键方面的研究项目。1)我们将利用eRASS x射线成像揭示星系群中热群内和环星系介质（IGrM； CGM）之间的相互作用。2)在XRISM发射后，我们将精确测量星系团内的热中速，并与现有紫外吸收线观测的冷相H I速度分布进行比较，以表征高速多相气体流动。3)展望未来，我们将采用最先进的星系形成模拟来生成CGM中空间重合区域的模拟x射线微热量计光谱和模拟紫外吸收和发射光谱。然后，我们将把这些专业知识传播给我们的新密歇根州立大学天文系，因为x射线观测被用于新密歇根州立大学教师研究的天文学的每个子领域，但x射线在我们的观测技能组合中是缺失的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The brilliant spiral appearances of galaxies have dazzled humanity since their discovery through the first telescopes. However, this picture of galaxies is highly incomplete, containing only their starlight. Those stars, like our Sun must form out of an enormous gas supply, both inside and outside the galaxy, that cannot be seen in light visible by human eyes. Thus, understanding how and why new generations of stars may or may not form (i.e., whether galaxies 'live' or 'die') requires observations over an enormous range of wavelengths, as the gas reservoirs in and around galaxies may span a factor of 100,000 in temperature. We now know that gas flows in and out of galaxies engage in a complex interplay, like ecosystems often encountered in nature. The mechanics of these ecosystems lies at the core of our own cosmic origins. The National Academy of Sciences has set these 'cosmic ecosystems' as a key national priority for astrophysics research over the next decade and beyond. The Principal Investigator's (PI) research group has been focused on the cooler gas in cosmic ecosystems, those detectable at ultraviolet and visible wavelengths, but the hotter phases requiring X-rays to observe play a critical role. This fellowship will equip the PI's research group at New Mexico State University to address this national priority from a comprehensive multi-wavelength perspective. The project will leverage the X-ray expertise at the NASA Goddard Space Flight Center to train the PI and a graduate student in X-ray astronomical observations. The research team will engage in three key investigations that couple our current expertise with the newly acquired X-ray techniques while employing X-ray facilities receiving substantial U.S. investment.The gas permeating cosmic ecosystems has been primarily characterized observationally at ultraviolet (UV) and optical wavelengths, which are sensitive to cool (10^4 K) and warm-hot (10^5−10^6 K) gas. However, galaxy formation theory is increasingly pointing towards the hotter phases ( 10^6 K) observed in X-rays as holding the answers to the critical processes within cosmic ecosystems. We stand at an exciting juncture with the imminent data release of the eROSITA All Sky Survey (eRASS), the U.S.- and Japanese-led high spectral resolution XRISM X-ray telescope launching in 2023, and the X-ray community tirelessly developing mission concepts for the next X-ray space telescope to be launched by the U.S. within the next decade (another National Academy recommendation). In partnership with astrophysicists at NASA Goddard Space Flight Center, the research team will build the necessary research infrastructure at New Mexico State University (NMSU) to seize these emerging opportunities. Towards this end, we will conduct research projects that involve the key facets of X-ray analysis. 1) We will employ the eRASS X-ray imaging to unveil the interactions between the hot intragroup and circumgalactic medium (IGrM; CGM) in galaxy groups. 2) After the launch of XRISM, we will measure precise hot intracluster medium velocities within galaxy clusters and compare with the cool-phase H I velocity distribution from existing UV absorption line observations to characterize high-velocity, multiphase gas flows. 3) Looking towards the future, we will employ state-of-the-art galaxy formation simulations to generate mock X-ray microcalorimeter spectra and mock UV absorption and emission spectra of spatially coincident regions in the CGM. We will then propagate this expertise back through our NMSU Astronomy Department, as X-ray observations are used in every subfield of astronomy studied by the NMSU faculty, but X-rays are missing from our observational skill portfolio.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.