ALFALFA：寻找（几乎）暗星系及其空间分布
ALFALFA: The Search for (Almost) Dark Galaxies and their Space Distribution
摘要：
Arecibo Legacy Fast ALFA巡天（ALCAFA）旨在探索z=0 HI质量函数（HIMF）在宇宙学上的重要体积。通过结合深度、宽区域和质心精度，ALCARFA将改进先前的HIMF测定，后者在大多数情况下允许立即识别每个HI信号的光学对应物。ALOCHFA将探测数百个HI质量小于10**7.5太阳质量和大于10**10.5太阳质量的星系，其最终目录将允许调查HIMF对局部密度和星系形态的依赖性。阿尔法已经证实了以前的建议，没有宇宙学意义上的人口丰富的HI暗星系。不到3%的河外HI源和< 1% of ones with HI masses >10**9.5太阳质量不能与恒星对应物识别。在双鱼座-英仙座超星系团前方的虚空中存在富含气体的矮星的初步结果表明，与数值模拟的预测相比，这种天体的数量不足。具有最高HI质量的物体表现出一系列的形态和光学颜色和表面亮度，但都似乎是大规模的磁盘系统。后者代表人口可能占主导地位的未来研究HI在更高的红移与平方公里阵列。
英文摘要：
The Arecibo Legacy Fast ALFA (ALFALFA) survey is designed to explore the z=0 HI mass function (HIMF) over a cosmologically significant volume. ALFALFA will improve on previous determinations of the HIMF by its combination of depth, wide area and centroiding accuracy, the latter allowing, in most cases, immediate identification of the optical counterpart to each HI signal. ALFALFA will detect hundreds of galaxies with HI masses less than 10**7.5 solar masses and also greater than 10**10.5 solar masses, and its final catalog will allow investigation of the dependence of the HIMF both on local density and on galaxy morphology. Already ALFALFA confirms previous suggestions that there is no cosmologically significant population of HI-rich dark galaxies. Fewer than 3% of all extragalactic HI sources and < 1% of ones with HI masses > 10**9.5 solar masses cannot be identified with a stellar counterpart. Very preliminary results on the presence of gas-rich dwarfs in the void in front of the Pisces-Perseus supercluster suggest an underabundance of such objects compared to the predictions of numerical simulations. The objects with highest HI mass exhibit a range of morphologies and optical colors and surface brightnesses but all appear to be massive disk systems. The latter represent the population likely to dominate future studies of HI at higher redshift with the Square Kilometer Array.
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