21 centimeter survey of luminous infrared galaxies

Abstract

The results from an Arecibo 21 cm survey of an unbiased sample of the most luminous far-infrared galaxies in the local universe (z < 0.1) are reported. Ninety-two galaxies with far-infrared luminosities in the range of 2 x 1010 Lq < Lfir < 2 x 1012 Lq were surveyed: 88 were detected in the 21 cm line of atomic hydrogen, and the radio continuum flux was determined for 80 galaxies in the sample. There is a correlation between the radio continuum and the far-infrared emission in this sample of galaxies. A high fraction of the H i profiles have structures that are indicative of large-scale dynamical disruptions. The masses of atomic hydrogen are in the range of 5 x 108 M0 to 3 x IO10 M© and are only loosely correlated with the far-infrared luminosities. A striking result from this survey is that 20% of the H i profiles show absorption features extending over several hundred km s_1, up to 1000 km s_1, with total column densities up to 1022 atoms cm2. The rate of detection of H i absorption increases with increasing far-infrared luminosity, and in the most luminous objects there is strong evidence for large amounts of turbulent atomic gas concentrated in the nuclear regions. As in galaxies with active nuclei and quasars, luminous infrared galaxies show a net statistical offset of the optical radial velocities relative to the systemic velocities determined from the 21 cm line observations.