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

在这个合作研究项目中。Snezana Stanimirovic（威斯康星大学麦迪逊分校）、Mary Putman（密歇根大学）和Eric Korpela（加州大学伯克利分校）将在整个阿雷西博天文台（13000平方度）的天空中调查银河系的中性氢（HI）。该项目将揭示银河系中性氢（HI）的详细空间和运动结构，并允许完成对气态盘、晕和它们之间物质流动的新研究。直到最近，阿雷西博l波段馈电阵列（ALFA）的安装才使整个阿雷西博天空的勘测成为可能，这是一个由7个接收器组成的集群，工作在21厘米的波长上，提供了无与伦比的灵敏度、分辨率和制图速度的组合。该调查已经揭示的主题有：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。在银河系盘中，阿雷西博的高分辨率观测结果，与其他星际示踪剂相比，探测了没有被一氧化碳追踪到的分子气体的性质，即所谓的“暗气体”。此外，HI数据集的统计调查将星际湍流的性质与潜在的物理条件联系起来。阿雷西博观测到的银盘和银晕之间的过渡区域，是由大量冷的、离散的HI云组成的厚“带”。这次调查将绘制出这个带的范围，并研究它与银河系盘和星系喷泉模型中恒星形成的局部位置的可能联系。在银晕本身，研究将集中在被称为高速云（HVCs）的HI晕云与周围弥散晕气体之间的相互作用。这将通过在日晕模型的背景下研究云的详细特征，并将云动力学直接与模拟进行比较来完成。初步调查数据还显示，阿雷西博将很好地对未开发的HVC人群进行抽样。该项目的核心是协同研究银河HI与其他波长的调查以及星际介质和气体晕的最新数值模拟。这个银河HI调查，面对理论和数值模拟，承诺对我们理解银河系中从几个pc到许多kpc尺度上的物质循环做出根本性的贡献。本次调查的数据产品将具有真正的传统特征，因为数据集的观测、数据简化和最终整理已经成功开发，并且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系研究的基础设施。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天空的图像将在三个机构的外展中心展出，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.