OH Megamasers and Galaxy Evolution

AST 0098526 Giovanelli许多星系的核都具有高能量的过程，这些过程被认为最终是由超大质量黑洞周围区域的强大引力场提供动力的。 在特殊的情况下，环绕或落入星系核区域的气体可以产生一个发光的微波激射器（微波激光），它被观测为从星系核发出的强射电谱线。 这种“超脉泽”--之所以这么叫是因为它们的亮度比银河系中发现的年轻恒星的典型脉泽大约高出一百万倍--是由激发的H2O或OH分子产生的。 特别是OH超脉泽，它们只存在于合并星系的核中，而且亮度足以在宇宙学距离上观测到。 这里提出的研究旨在描述和理解合并星系和OH超脉泽的产生之间的关系，最终目标是使用OH超脉泽追踪星系合并历史作为宇宙时间的函数。 星系数量随时间的演化尚不清楚，尽管它很可能是星系演化过程中的一个重要元素。 这项研究将（1）从阿雷西博天文台合并星系的宽OH谱线调查中建立OH超脉泽的空间密度，（2）从谱线强度变化的研究中确定这些系统中OH脉泽的空间尺度，（3）从帕洛马天文台的光谱学中表征最有利于产生OH超脉泽的宿主类型，（4）OH超脉泽作为高红移星系合并指示器的潜在用途。 ***

AST 0098526Giovanelli The nuclei of many galaxies harbor highly energetic processes, which are thought to be powered ultimately by strong gravitational fields in the regions surrounding supermassive black holes. In special circumstances, gas orbiting or falling into the nuclear regions of galaxies can produce a luminous maser (a microwave laser) which is observed as a strong radio spectral line emanating from a galactic nucleus. Such "megamasers" --- so called because they are roughly a million times more luminous than typical masers associated with young stars found in the Milky Way --- are produced by excited H2O or OH molecules. OH megamasers in particular are foundonly in the nuclei of merging galaxies and are luminous enough to be observable at cosmological distances. The study proposed here aims to characterize and understand the relationship between merging galaxies and the production of OH megamasers with the ultimate goal of using OH megamasers to trace the merging history of galaxies as a function of cosmic time. The number evolution of galaxies with time is not yet known, although it is likely to be an important element in the galaxy evolution process. This study will (1) establish the space density of OH megamasers from a broad OH spectral line survey of merging galaxies at the Arecibo Observatory, (2) determine the spatial scale of OH masing in these systems from a study of line intensity variability, (3) characterize the type of host most favorable to producing an OH megamaser from optical spectroscopy at Palomar Observatory, and (4) characterize the potential use of OH megamasers as indicators of merging galaxies at high redshift. ***