OH Megamasers and Galaxy Evolution

AST 0098526Giovanelli 许多星系的核心都蕴藏着高能过程，人们认为这些过程最终是由超大质量黑洞周围区域的强引力场提供动力的。 在特殊情况下，绕行或落入星系核区域的气体可以产生发光微波激射器（微波激光），其被观察为从星系核发出的强射电谱线。 这种“巨型微波激射”——之所以如此称呼，是因为它们的亮度大约比银河系中发现的年轻恒星相关的典型微波激射强一百万倍——是由激发的 H2O 或 OH 分子产生的。 特别是 OH 巨型漩涡仅存在于合并星系的核中，并且亮度足以在宇宙学距离上观测到。 这里提出的研究旨在表征和理解合并星系与 OH 巨型微波激射器产生之间的关系，最终目标是使用 OH 巨型微波激射器来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)通过阿雷西博天文台合并星系的广泛OH谱线调查确定OH巨型微波激射器的空间密度，(2)通过线强度变异性研究确定这些系统中OH巨型微波激射器的空间尺度，(3)通过帕洛马天文台的光谱学表征最有利于产生OH巨型微波激射器的宿主类型，以及(4)表征OH巨型微波激射器作为合并指标的潜在用途高红移的星系。 ***

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. ***