Neutral hydrogen in compact groups of galaxies

Abstract

view Abstract Citations (109) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutral Hydrogen in Compact Groups of Galaxies Williams, B. A. ; Rood, Herbert J. Abstract Integrated H I profiles were detected for 34 of 51 Hickson compact groups (HCGs) of galaxies, and sensitive upper limits to the H I flux density were measured for the other 17. About 60 percent of the galaxies within compact groups are spirals, and a significant tendency exists for the fraction of elliptical galaxies to increase with group surface brightness. The amount of dark matter within the compact group region is negligibly small. An HCG on average contains half as much neutral hydrogen as a loose group with a similar spectrum of galaxy luminosities and morphological types, implying that compact groups are independent dynamical entities and not transient or projected configurations of loose groups. The observed fraction of galaxies which are luminous enough to be possible merger products of compact groups is small compared with the fraction required by the theory of dynamical friction. A clear discrepancy thus exists between solid empirical evidence and a straightforward prediction of Newtonian dynamical theory in a setting which does not permit a dark matter explanation. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1987 DOI: 10.1086/191165 Bibcode: 1987ApJS...63..265W Keywords: Astronomical Spectroscopy; Galactic Clusters; Hydrogen Clouds; Neutral Gases; Radio Galaxies; Centimeter Waves; Galactic Rotation; Galactic Structure; Radiant Flux Density; Spectral Line Width; Visible Spectrum; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: STRUCTURE; RADIO SOURCES: GALAXIES; RADIO SOURCES: 21 CM RADIATION full text sources ADS | data products SIMBAD (513) NED (509)