1999/06/08 by G. D. Banks, M. J. Disney, P. M. Knezek +38 · 3 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Centaurus A #Dwarf galaxy #Dwarf galaxy problem #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy group #Group (periodic table) #Local Group #Luminous infrared galaxy #Physics #Sky #Stellar, planetary, and galactic studies #Surface brightness #astro-ph
paper · pdf · doi:10.1086/307854
19 pages Latex, 6 figures (Fig. 2 in four parts, Fig.5 in two parts). To appear in The Astrophysical Journal (Vol. 524, October 1999)
arxiv created 1999/06/08 · openalex publication_date 1999/10/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 deg 2 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 10 7 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 M = 2.1 × 10 8 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 ( M B > -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 10 7 M ☉ < M < 10 9 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.