Rotation and masses of galaxies as determined by single spacing interferometry of 21 CM hydrogen emission

Abstract

A total of 79 galaxies have been investigated with the Owens Valley Observatory's two-element interferometer for content of neutral hydrogen. The baseline used was 100 feet east-west, and the filter bandwidth was 100 kHz. Thirty of the galaxies had detectable emission (> 0.5 f.u.). The results are presented as line and position profiles for each galaxy (i.e.plots of the flux, and its position derived from the interferometer phase as a function of radial velocity). An extensive investigation of model profiles is also presented for the purposes of interpretation of the observed results. It is shown that while in most cases the position profile cannot be directly interpreted as the rotation curve, the model analysis does suggest a method for estimating the rotational characteristics of the galaxies from the profiles. Using the estimated rotational parameters, total masses were calculated and are presented along with other quantities derivable from the profiles, such as the galaxy radial velocities and estimates of the neutral hydrogen masses. All of the irregular galaxies that were detected were found to be rotating, with the exception of WLM, which was inconclusive.