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arXiv · 1008.5107

The Arecibo Legacy Fast ALFA Survey: X. The HI Mass Function and Omega_HI From the 40% ALFALFA Survey

Ann M. Martin·Emmanouil Papastergis·Riccardo Giovanelli·Martha P. Haynes·Christopher M. Springob·Sabrina Stierwalt
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Abstract

The Arecibo Legacy Fast ALFA (ALFALFA) survey has completed source extraction for 40% of its total sky area, resulting in the largest sample of HI-selected galaxies to date. We measure the HI mass function from a sample of 10,119 galaxies with 6.2 < log (M_HI/M_Sun) < 11.0 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 HIMF with both the 1/Vmax 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 phi* = 4.8 (+/- 0.3) * 10^-3, log (M*/M_Sun) + 2 log(h_70) = 9.96 (+/- 0.2), and alpha = -1.33 (+/- 0.02). We find Omega_HI = 4.3 (+/- 0.3) * 10^-4, 16% larger than the 2005 HIPASS result, and our Schechter function fit extrapolated to log (M_HI/M_Sun) = 11.0 predicts an order of magnitude more galaxies than HIPASS. The larger values of Omega_HI and of M* imply an upward adjustment for estimates of the detection rate of future large-scale HI 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 HI-selected halos indicates that the disagreement between dark matter mass functions and baryonic mass functions may soon be resolved.

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Ann M. Martin, Emmanouil Papastergis, Riccardo Giovanelli, Martha P. Haynes, Christopher M. Springob, Sabrina Stierwalt. 2010-08-30. The Arecibo Legacy Fast ALFA Survey: X. The HI Mass Function and Omega_HI From the 40% ALFALFA Survey. https://doi.org/10.1088/0004-637x%2F723%2F2%2F1359

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