Harvesting ALFALFA: Tracking the Gas-Rich Halos at z=0

星系最初是如何形成的，以及它们在整个生命周期中是如何变化的，这是天体物理学中最不为人所知的问题之一。许多项目都以解开这些谜团为中心。该项目旨在提供第一个在宇宙学上具有重要意义的富含气体的晕的强大普查，并打算提供重要的见解，了解一些大质量星系如何在不将气体转化为恒星的情况下保持巨大的气藏，以及孤立的低质量晕如何能够保留一些原子氢气，尽管它们的热状态脆弱且潜力井浅。这一建议旨在结束已经开始的调查，以前由国家科学基金会资助。可以理解的是，这项调查的结论主要是由于望远镜停飞而推迟的，但应该会在2012年秋天得出结论。这项调查是在阿雷西博射电望远镜上进行的，使用阿雷西博l波段馈电阵列（ALFA），阿雷西博传统快速馈电阵列（ALFALFA）。该调查已经产生了远远超过该领域先前调查的结果，调查结果将有助于表征此类光晕的质量函数，并允许与当前λ - cdm范式下的宇宙理论模拟进行直接比较。ALFALFA是一项银河系外高分辨率21厘米线测量，将识别出在银河系高纬度天空7000平方度至z 0.06的高分辨率天体。公共ALFALFA数据库包括HI线光谱和HI线位置、红移、速度宽度和通量密度的目录，以及最可能的光学对应的其他数字数据集的坐标和交叉识别。这个项目也有更广泛的教育影响。研究生将密切参与项目的所有阶段，帮助规划和执行观测程序，开发数据处理和分析软件，生产公共数据产品，与虚拟天文台对接，以及承担自己的科学项目。作为该项目的一部分编写的教育材料将通过现有的ALFALFA公共网站提供。

Precisely how galaxies initially form and how they change throughout their lifetime are among the least understood problems in astrophysics. Many projects are centered on unraveling these mysteries. This project aims to provide the first robust census of gas-rich halos over a cosmologically significant volume and intends to provide important insight into how some massive galaxies maintain huge gas reservoirs without converting their gas into stars and how isolated low mass halos are able to retain some atomic hydrogen gas despite their fragile thermal state and shallow potential wells. This proposal is intended to conclude the already initiated survey, previously funded by NSF. The conclusion of the survey was understandably delayed primarily by telescope downtime but should conclude by the fall of 2012.The survey is conducted at the Arecibo radio telescope and uses the Arecibo L-band Feed Array (ALFA), the Arecibo Legacy Fast ALFA (ALFALFA). The survey has already produced results far exceeding the previous survey in this field, and the survey results will help to characterize the mass function of such halos and allow direct comparison with theoretical simulations of Universe in the current Lambda-CDM paradigm. ALFALFA, an extragalactic HI 21 cm line survey, will identify HI-bearing objects found over 7000 square degrees of the high galactic latitude sky out to z 0.06. The public ALFALFA database includes HI line spectra and catalogues of HI line positions, redshifts, velocity widths, and flux densities as well as coordinates and cross-identifications in other digital data sets of the most probable optical counterparts.This project has educational broader impacts as well. Graduate students will be intimately involved in all phases of the project, helping to plan and execute the observing program, developing software for data processing and analysis, producing public data products and interfacing with the Virtual Observatory, as well as undertaking their own science projects. Educational materials that are developed as part of this project will be made available through the existing ALFALFA public web site.