We review the results of HI line surveys of extragalactic sources in the local Universe. In the last two decades major efforts have been made in establishing on firm statistical grounds the properties of the HI source population, the two most prominent being the HI Parkes All Sky Survey and the Arecibo Legacy Fast ALFA survey. We review the choices of technical parameters in the design and optimization of spectro-photometric “blind” HI surveys, which for the first time produced extensive HI-selected data sets. Particular attention is given to the relationship between optical and HI populations, the differences in their clustering properties and the importance of HI-selected samples in contributing to the understanding of apparent conflicts between observation and theory on the abundance of low mass halos. The last section of this paper provides an overview of currently ongoing and planned surveys which will explore the cosmic evolution of properties of the HI population.

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河外HI调查

我们回顾了本地宇宙中河外源的 HI 线调查结果。在过去的 20 年中，在确定 HI 源种群的属性方面做出了重大努力，其中两个最突出的是 HI Parkes All Sky Survey 和 Arecibo Legacy Fast ALFA 调查。我们回顾了分光光度“盲”HI 调查的设计和优化中技术参数的选择，这是第一次产生广泛的 HI 选择数据集。特别关注光学和 HI 种群之间的关系、它们的聚类特性的差异以及 HI 选择的样本在有助于理解观测与低质量晕丰度理论之间的明显冲突方面的重要性。