Collaborative Research: Mapping the Galactic Arecibo Sky in the 21-cm Line

在这个合作研究项目中，威斯康星大学麦迪逊分校的斯内扎纳·斯塔米罗维奇博士、密歇根大学的玛丽·普特曼博士和加州大学伯克利分校的埃里克·科佩拉博士将在整个阿雷西博天文台天空(13,000平方度)上测量中性氢(HI)中的银河系。这个项目将揭示银河系中性氢(HI)的详细空间结构和运动学结构，并使对气态盘、晕以及它们之间的物质流动的新研究得以完成。直到最近，随着阿雷西博L波段馈电阵列(ALFA)的安装，测量整个阿雷西博天空才成为可能，该阵列由七个接收器组成，在21厘米的波长下工作，提供无与伦比的灵敏度、分辨率和测绘速度的组合。调查已经发现的主题是：1)原子云和分子云之间的演化，2)银盘和晕之间的相互作用，以及3)在银晕中工作的详细气体动力学。在银盘中，与其他星际示踪器相比，高分辨率的阿雷西博观测探测到了未被一氧化碳追踪的分子气体的性质，即所谓的“暗气体”。此外，HI数据集的统计研究将把星际湍流的特性与基本的物理条件联系起来。在阿雷西博的观测中，银盘和晕之间的过渡区由许多寒冷的、离散的HI云组成的一条厚厚的“带”组成。这项调查将绘制出这条带的范围，并调查它与银河盘和星系喷泉模型中恒星形成的局部地点的可能联系。在银晕本身，研究将集中在被称为高速云(HVC)的HI晕云与周围扩散的晕气体之间的相互作用。这将通过在光晕模型的背景下研究云的详细特征，并将云的动力学直接与模拟进行比较来实现。初步调查数据还显示，阿雷西博将极好地采样尚未勘探的HVC人群的尾部。该项目的核心是对银河HI的协同研究，以及其他波长的测量，以及对星际介质和气态晕的最新数值模拟。这次银河HI调查面临着理论和数值模拟，有望为我们理解从几个PC到许多千分之一的尺度上银河系中物质的循环做出根本贡献。这次调查的数据产品将具有真正的遗产性质，因为数据立方体的观测、数据简化和最终整理已经成功开发，这些最终数据产品将及时向公众提供。这些数据产品的传播，将加强世界各地银河研究的基础设施。这项研究将为加州大学伯克利分校、密歇根大学和威斯康星大学麦迪逊分校的博士论文和本科生研究项目提供主题，促进研究和教育的融合。银河HI星空的图像将在这三个机构的推广中心展出，向公众展示银河系的多波长特征。

In this collaborative research project Drs. Snezana Stanimirovic (University of Wisconsin - Madison), Mary Putman (University of Michigan), and Eric Korpela (University of California - Berkeley) will survey the Galaxy in neutral hydrogen (HI) across the entire Arecibo Observatory sky (13,000 square degrees). This project will reveal the detailed spatial and kinematic structure of Galactic neutral hydrogen (HI) and allow new studies of the gaseous disk, halo, and the flow of material between them to be completed. Surveying the entire Arecibo sky has only recently become possible with the installment of the Arecibo L-band Feed Array (ALFA), a cluster of seven receivers operating at the wavelength of 21-cm that provide an unsurpassed combination of sensitivity, resolution, and mapping speed. Topics already being uncovered by the survey are: 1) the evolution between atomic and molecular clouds, 2) the interplay between the Galactic disk and halo, and 3) the detailed gas dynamics at work in the Galactic halo. In the Galactic disk, the high-resolution Arecibo observations, when compared with other interstellar tracers, probe the nature of the molecular gas not traced by carbon monoxide, the so called "dark gas". In addition, statistical investigation of HI datasets will relate properties of interstellar turbulence with the underlying physical conditions. The transition region between the Galactic disk and halo, when viewed by Arecibo, consists of a thick "belt" of numerous cold, discrete HI clouds. The survey will map the extent of this belt and investigate its possible connection to the local sites of star formation in the Galactic disk and galactic fountain models. In the Galactic halo itself, research will focus on the interaction between HI halo clouds known as high-velocity clouds (HVCs) and the surrounding diffuse halo gas. This will be done by studying the detailed features of the clouds in the context of models of the halo and comparing the cloud dynamics directly to simulations. The initial survey data also show that Arecibo will superbly sample the unexplored tail-end of the HVC population. At the heart of this project are synergistic studies of Galactic HI with surveys at other wavelengths and the latest numerical simulations of the interstellar medium and gaseous halo. This Galactic HI survey, confronted with theory and numerical simulations, promises fundamental contributions to our understanding of the cycling of matter in the Galaxy on scales from a few pc to many kpc.The data products from this survey will have a true legacy character, as the observations, data reduction, and final collating of the data cubes have been successfully developed, and these final data products will be made available to the public on a timely basis. The dissemination of these data products, will enhance the infrastructure for Galactic research across the world. This research will provide topics for Ph.D. theses and undergraduate research projects at the University of California-Berkeley, the University of Michigan, and the University of Wisconsin-Madison, fostering the confluence of research and education. Images of the Galactic HI sky will be displayed at outreach centers at the three institutions to demonstrate the multi-wavelength character of the Galaxy to the public.