The Arecibo Legacy Fast ALFA Survey. X. The H I Mass Function and from the 40% ALFALFA Survey

• Published in: The Astrophysical journal Vol. 723; no. 2; pp. 1359 - jQuery1323913593145='48'
• Main Authors: Martin, Ann M, Papastergis, Emmanouil, Giovanelli, Riccardo, Haynes, Martha P, Springob, Christopher M, Stierwalt, Sabrina
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 10.11.2010
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BARYONS; DWARF STARS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; FERMIONS; GALAXIES; HADRONS; INTERFERENCE; LUMINOSITY; MASS; MATTER; NONLUMINOUS MATTER; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; RADIATIONS; RADIOWAVE RADIATION; RED SHIFT; STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/723/2/1359

The Arecibo Legacy Fast ALFA (ALFALFA) survey has completed source extraction for 40% of its total sky area, resulting in the largest sample of H I-selected galaxies to date. We measure the H I mass function from a sample of 10,119 galaxies with and with well-described mass errors that accurately reflect our knowledge of low-mass systems. We characterize the survey sensitivity and its dependence on profile velocity width, the effect of large-scale structure, and the impact of radio frequency interference in order to calculate the H I mass function with both the 1/V max and 2DSWML methods. We also assess a flux-limited sample to test the robustness of the methods applied to the full sample. These measurements are in excellent agreement with one another; the derived Schechter function parameters are * (h 3 70 Mpc--3 dex--1) = 4.8 ? 0.3 X 10--3, log (M */M ) + 2 log h 70 = 9.96 ? 0.02, and Delta *a = --1.33 ? 0.02. We find 4.3 ? 0.3 X10--4 h --1 70, 16% larger than the 2005 HIPASS result, and our Schechter function fit extrapolated to = 11.0 predicts an order of magnitude more galaxies than HIPASS. The larger values of and of M * imply an upward adjustment for estimates of the detection rate of future large-scale H I line surveys with, e.g., the Square Kilometer Array. A comparison with simulated galaxies from the Millennium Run and a treatment of photoheating as a method of baryon removal from H I-selected halos indicate that the disagreement between dark matter mass functions and baryonic mass functions may soon be resolved.