New galaxies discovered in the first blind H I survey of the Centaurus A group

G. D. Banks*, M. J. Disney, P. M. Knezek, H. Jerjen, D. G. Barnes, R. Bhatal, W. J. G. De Blok, P. J. Boyce, R. D. Ekers, K. C. Freeman, B. K. Gibson, P. A. Henning, V. Kilborn, B. Koribalski, R. C. Kraan-Korteweg, D. F. Malin, R. F. Minchin, J. R. Mould, T. Oosterloo, R. M. PriceM. E. Putman, S. D. Ryder, E. M. Sadler, L. Staveley-Smith, I. Stewart, F. Stootman, R. A. Vaile, R. L. Webster, A. E. Wright

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)


We have commenced a 21 cm survey of the entire southern sky (δ < 0°, -1200 km s-1 < v < 12,700 km s-1) that is "blind," i.e., unbiased by previous optical information. In the present paper we report on the results of a pilot project that is based on data from this all-sky survey. The project was carried out on an area of 600 deg2 centered on the nearby Centaurus A (Cen A) group of galaxies at a mean velocity of v ∼ 500 km s-1. This was recently the subject of a separate and thorough optical survey. We found 10 new group members to add to 21 galaxies already known in the Cen A group: five of these are previously uncataloged galaxies, while five were previously catalogued but not known to be associated with the group. Most of the new members have H I masses close to our survey limit of 107 M at the assumed group distance of 3.5 Mpc. The new detection with the largest H I mass is ESO 174-G?001 with MH I = 2.1 × 108 M. Prior to our survey this galaxy was an uncertain optical identification because of high Galactic extinction. We found optical counterparts for all the H I detections, most of them intrinsically very faint (MB>-13.0), low surface brightness dwarf galaxies with H I profile line-widths suggestive of dynamics dominated by dark matter. The new group members add approximately 6% to the H I mass of the group and 4% to its light. The H I mass function, derived from all the known group galaxies in the interval 107 M < MH I < 109 M, has a faint-end slope of 1.30 ± 0.15, allowing us to rule out a slope of 1.7 at 95% confidence. Even if the number in the lowest mass bin is increased by 50%, the slope only increases to 1.45 ± 0.15.

Original languageEnglish
Pages (from-to)612-622
Number of pages11
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 20 Oct 1999
Externally publishedYes


  • Galaxies: Clusters: Individual (Centaurus A)
  • Galaxies: Distances and redshifts
  • Galaxies: ISM
  • Radio lines: Galaxies
  • Surveys


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