标题： 阿雷西博遗产快速ALFA巡天：alpha.40 HI源目录，其特性及其对HI质量函数推导的影响 显示英文标题

标题： The Arecibo Legacy Fast ALFA Survey: The alpha.40 HI Source Catalog, its Characteristics and their Impact on the Derivation of the HI Mass Function

摘要： 我们呈现了一个当前的21厘米HI线源目录，该目录是从Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA)调查中提取的，覆盖约2800平方度的天空：alpha.40目录。覆盖最终调查区域的40%，alpha.40目录包含15855个源，在区域07h30m < R.A. < 16h30m，+04度 < Dec. < +16度和+24度 < Dec. < +28度以及22h < R.A. < 03h，+14度 < Dec. < +16度和+24度 < Dec. < +32度。其中，15041个源肯定是星系外的，产生每平方度5.3个星系的源密度，比从HI Parkes All Sky Survey提取的目录提高了29倍。除了源中心位置、HI线通量密度、退行速度和线宽外，目录还包括每个HI线检测最可能的光学对应物的坐标，并且单独汇编提供了与斯隆数字天空调查数据发布7相关的光度和光谱目录中给出的识别的交叉匹配。少于2%的星系外HI线源无法与可行的光学对应物进行识别；其中一些可能是红移0.16 < z < 0.25之间的稀有OH巨脉泽。对当前alpha.40目录的完整性、宽度依赖灵敏度函数和固有偏差进行了详细分析。评估了调查选择、距离误差、当前体积覆盖范围和局部大尺度结构对推导HI质量函数的影响。虽然alpha.40目前尚未提供宇宙体积的完全代表性采样，但使用ALFALFA未来数据发布推导的HI质量函数将进一步改善统计和系统不确定性。 显示英文摘要

摘要： We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800 square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A. < 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A. < 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041 are certainly extragalactic, yielding a source density of 5.3 galaxies per square degree, a factor of 29 improvement over the catalog extracted from the HI Parkes All Sky Survey. In addition to the source centroid positions, HI line flux densities, recessional velocities and line widths, the catalog includes the coordinates of the most probable optical counterpart of each HI line detection, and a separate compilation provides a crossmatch to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width dependent sensitivity function and bias inherent in the current alpha.40 catalog. The impact of survey selection, distance errors, current volume coverage and local large scale structure on the derivation of the HI mass function is assessed. While alpha.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the HI mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties.