The H I mass function of the Local Universe: Combining measurements from HIPASS, ALFALFA, and FASHI

March 2025 • 2025A&A...695A.241M

Authors • Ma, Wenlin • Guo, Hong • Xu, Haojie • Jones, Michael G. • Zhang, Chuan-Peng • Zhu, Ming • Wang, Jing • Wang, Jie • Jiang, Peng

Abstract • We present the first H I mass function (HIMF) measurement for the recent FAST All Sky H I (FASHI) survey and the most complete measurements of the HIMF in the Local Universe thus far. We obtained these results by combining the H I catalogues from H I Parkes All Sky Survey (HIPASS), Arecibo Legacy Fast ALFA (ALFALFA), and FASHI surveys at a redshift of 0 < z < 0.05, covering 76% of the entire sky. We adopted the same methods to estimate the distances, calculate the sample completeness, and determine the HIMF for all three surveys. The best-fit Schechter function for the total HIMF shows a low-mass slope parameter of α = −1.30 ± 0.01 and a 'knee' mass of log(M_s/h₇₀⁻² M_⊙) = 9.86 ± 0.01, along with a normalisation of ϕ_s = (6.58 ± 0.23)×10⁻³ h₇₀³ Mpc⁻³ dex⁻¹. This gives us the cosmic H I abundance: Ω_{H I} = (4.54 ± 0.20) × 10⁻⁴ h₇₀⁻¹. We find that a double Schechter function with the same slope α better describes our HIMF, where the two different 'knee' masses are log(M_s1/h₇₀⁻² M_⊙) = 9.96 ± 0.03 and log(M_s2/h₇₀⁻² M_⊙) = 9.65 ± 0.07. We verify that the measured HIMF is marginally affected by the choice of distance estimates. The effect of cosmic variance is significantly suppressed by combining the three surveys and this provides a unique opportunity to obtain an unbiased estimate of the HIMF in the Local Universe.

Links

• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202452976/postscript
• PDF https://www.aanda.org/10.1051/0004-6361/202452976/pdf
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2025A%26A...695A.241M
• PREPRINT http://arxiv.org/abs/2411.09903
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202452976