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The H I mass function and velocity width function of void galaxies in the Arecibo Legacy Fast ALFA Survey
Journal article   Open access

The H I mass function and velocity width function of void galaxies in the Arecibo Legacy Fast ALFA Survey

Crystal M. Moorman, Michael S. Vogeley, Fiona Hoyle, Danny C. Pan, Martha P. Haynes and Riccardo Giovanelli
Monthly notices of the Royal Astronomical Society, v 444(4), pp 3559-3570
11 Nov 2014
DOI: https://doi.org/10.1093/mnras/stu1674
url
http://arxiv.org/abs/1408.3392View
SubmittedOpen Access (License Unspecified),  Open

Abstract

Astronomy & Astrophysics Physical Sciences Science & Technology
We measure the HI mass function (HIMF) and velocity width function (WF) across environments over a range of masses, 7.2 < log (M-HI/M-circle dot) < 10.8, and profile widths, 1.3 log (km s(-1)) < log (W) < 2.9 log (km s(-1)), using a catalogue of similar to 7300 HI-selected galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) Survey, located in the region of sky where ALFALFA and Sloan Digital Sky Survey (Data Release 7) North overlap. We divide our galaxy sample into those that reside in large-scale voids (void galaxies) and those that live in denser regions (wall galaxies). We find the void HIMF to be well fitted by a Schechter function with normalization Phi* = (1.37 +/- 0.1) x 10(-2) y h(3) Mpc(-3), characteristic mass log(M-HI*/M-circle dot) + 2 log h(70) = 9.86 +/- 0.02, and low-mass-end slope alpha = -1.29 +/- 0.02. Similarly, for wall galaxies, we find best-fitting parameters Phi* = (1.82 +/- 0.03) x 10(-2) h(3) Mpc(-3), log(M-H I*/M-circle dot) + 2 log h(70) = 10.00 +/- 0.01, and alpha = -1.35 +/- 0.01. We conclude that void galaxies typically have slightly lower HI masses than their non-void counterparts, which is in agreement with the dark matter (DM) halo mass function shift in voids assuming a simple relationship between DM mass and HI mass. We also find that the low-mass slope of the void HIMF is similar to that of the wall HIMF suggesting that there is either no excess of low-mass galaxies in voids or there is an abundance of intermediate HI mass galaxies. We fit a modified Schechter function to the ALFALFA void WF and determine its best-fitting parameters to be Phi* = 0.21 +/- 0.1 h(3) Mpc(-3), log (W*) = 2.13 +/- 0.3, alpha = 0.52 +/- 0.5, and high-width slope beta = 1.3 +/- 0.4. For wall galaxies, the WF parameters are Phi* = 0.022 +/- 0.009 h(3) Mpc(-3), log (W*)= 2.62 +/- 0.5, alpha= -0.64 +/- 0.2, and beta = 3.58 +/- 1.5. Because of large uncertainties on the void and wall WFs, we cannot conclude whether the WF is dependent on the environment.

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