Quasars Probing Quasars

在类星体发现后的50年里，一幅关于这些神秘物体的图景出现了，其中类星体是位于大型星系中心的超大质量黑洞。黑洞的质量可能是太阳的数百万到数十亿倍。正如这幅图所暗示的那样，类星体现象与被称为“活动星系核”的物体是同一种现象。所有类星体的特征都是巨大的亮度，以至于类星体经常比其宿主星系中数十亿颗恒星发出的光都要亮。它们的极端亮度使得观测距离地球数十亿光年的类星体成为可能。由于光速有限，这意味着天文学家可以在宇宙早期观测类星体，即星系形成的时代。这个项目将专门研究类星体对。类星体对是相对罕见的，彼此之间没有物理上的联系。相反，它们是两个距离不同的类星体的叠加，在天空中看起来靠得很近。当距离较远的类星体发出的光经过距离较近的类星体时，宿主类星体所在星系的光晕中的任何气体，即所谓的“环星系介质”，都会在距离较远的类星体的光谱上留下印记，从而可以研究该气体的特征，并为宿主星系的形成机制提供线索。这组研究人员已经收集了这样的一对样本，并将利用它们来研究星系周围的气体以及星系之间的气体。该项目还将支持一所少数族裔大学的实习项目和公共宣传。这个项目是已经建立的类星体探测类星体项目在几个新的科学方向上的延伸，并支持天文学扩展到萨利纳斯山谷的西班牙裔社区。具体的科学重点将集中在大质量星系的环星系介质、AGN物理和红移约为2的星系间介质上。该项目将利用几乎所有大口径光学/近红外望远镜的数据，并将利用最先进的宇宙学模拟来解释结果和测试星系形成、类星体反馈、宇宙再电离和超大质量黑洞演化的理论。该项目的核心将是利用类星体对探测高红移的星系间和星系周围介质，并为解决类星体物理中的基本问题提供证据。典型的类星体对在物理上并不相互关联，但是来自背景类星体的光会被靠近的、红移较低的类星体的物质所印记。这样就可以测定任何吸收气体的结构尺寸及其密度、质量等。将支持三个不同但耦合的项目：(1)通过阐明类星体和亚毫米星系周围星系介质的特性来验证星系形成理论；(2)利用横向邻近效应估计活动星系现象的时间尺度；(3)首次测量了红移2附近星系间介质的小尺度结构。这是一个雄心勃勃的计划，PI和他的合作者拥有必要的物质资源（望远镜时间等）和智力实力。

In the fifty years since the discovery of quasars, a picture of these enigmatic objects has emerged wherein quasars are supermassive black holes residing at the centers of large galaxies. The black hole may have a mass of millions to billions times that of the sun. As this picture implies, the quasar phenomenon is one and the same as that of the objects referred to as "active galactic nuclei." All are characterized by enormous luminosity such that the quasar frequently outshines the light from all of the billions of stars in its host galaxy. Their extreme luminosity makes it possible to observe quasars located at billions of light-years from earth. Due to the finite speed of light, this means that astronomers can literally observe quasars at an earlier epoch in the universe, the age of the formation of galaxies. This project will specifically study pairs of quasars. Quasar pairs are relatively rare and are not physically associated with one another. Instead, they are a superposition of two quasars at different distances that appear close together on the sky. As the light from the more distant quasar passes by the nearer one, any gas in the halo of the galaxy hosting the latter quasar, the so-called "circumgalactic medium," imprints a signature on the spectrum of the more distant quasar, allowing the study of the characteristics of that gas and giving clues as to the mechanism of the formation of the host galaxy. This team of researchers has assembled a sample of such pairs and will use them to study the circumgalactic gas as well as the gas between galaxies. The project will also support internship programs at a minority-serving college and public outreach.This project is an extension of the well-established Quasars Probing Quasars project into several new scientific directions and support astronomical outreach into the Hispanic community of Salinas Valley. Specific scientific emphasis will be concentrated on the circumgalactic medium of massive galaxies, AGN physics, and the intergalactic medium at redshift of about 2. The project will utilize data from essentially every large-aperture, optical/near-IR telescope and will leverage state-of-the-art cosmological simulations to interpret results and test theories of galaxy formation, quasar feedback, cosmic re-ionization, and supermassive black hole evolution. The core of the project will be the use of pairs of quasars to probe the intergalactic and circumgalactic media at high redshift as well as to provide evidence for the resolution of fundamental questions in quasar physics. Typical quasar pairs are not physically associated with one another but the light from the background quasar is imprinted by material associated from the nearer, lower redshift member of the pair. This allows determination of the size of structure in any absorbing gas along with its density, mass, etc. Three distinct but coupled programs will be supported: (1) to test theories of galaxy formation by elucidating the properties of the circumgalactic medium around galaxies hosting quasars and sub-millimeter galaxies; (2) to estimate timescales for the active galaxy phenomenon using the transverse proximity effect; and (3) make the first measurements of the small scale structure of the intergalactic medium at redshifts around 2. This is an ambitious program for which the PI and his collaborators have the necessary physical resources (telescope time, etc.) and intellectual prowess.