The 1000 brightest HIPASS galaxies: The H I mass function and ΩH I

M. A. Zwaan*, L. Staveley-Smith, B. S. Koribalski, P. A. Henning, V. A. Kilborn, S. D. Ryder, D. G. Barnes, R. Bhathal, P. J. Boyce, W. J. G. De Blok, M. J. Disney, M. J. Drinkwater, R. D. Ekers, K. C. Freeman, B. K. Gibson, A. J. Green, R. F. Haynes, H. Jerjen, S. Juraszek, M. J. KestevenP. M. Knezek, R. C. Kraan-Korteweg, S. Mader, M. Marquarding, M. Meyer, R. F. Minchin, J. R. Mould, J. O'Brien, T. Oosterloo, R. M. Price, M. E. Putman, E. Ryan-Weber, E. M. Sadler, A. Schröder, I. M. Stewart, F. Stootman, B. Warren, M. Waugh, R. L. Webster, A. E. Wright

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

43 Citations (Scopus)


We present a new, accurate measurement of the H I mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest H I peak flux densities in the southern (δ < 0°) hemisphere. This sample spans nearly 4 orders of magnitude in H I mass [log (MH I/ M) + 2 log h75 = 6.8-10.6] and is the largest sample of H I-selected galaxies to date. We develop a bivariate maximum likelihood technique to measure the space density of galaxies and show that this is a robust method, insensitive to the effects of large-scale structure. The resulting H I mass function can be fitted satisfactorily with a Schechter function with faint-end slope α = -1.30. This slope is found to be dependent on morphological type, with late-type galaxies giving steeper slopes. We extensively test various effects that potentially bias the determination of the H I mass function, including peculiar motions of galaxies, large-scale structure, selection bias, and inclination effects, and we quantify these biases. The large sample of galaxies enables an accurate measurement of the cosmological mass density of neutral gas: ΩH I = (3.8 ± 0.6) × 10-4 h75-1. Low surface brightness galaxies contribute only ∼ 15% to this value, consistent with previous findings.

Original languageEnglish
Pages (from-to)2842-2858
Number of pages17
JournalAstronomical Journal
Issue number6
Publication statusPublished - 1 Jun 2003
Externally publishedYes


  • Galaxies: ISM
  • Galaxies: luminosity function, mass function
  • ISM: general
  • Radio emission lines
  • Surveys


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